Class 7, Maths

Class 7 : Maths โ€“ Lesson 3. A Peek Beyond the Point

EXPLANATION AND ANALYSIS

๐Ÿ”ต Introduction: Moving Beyond Whole Numbers

๐Ÿง  In earlier classes, we mostly worked with whole numbers and integers. However, many situations in daily life involve numbers that are not whole. For example, the length of a ribbon may be 2.5 metres, the weight of a packet may be 1.75 kilograms, or the time taken to complete a race may be 3.2 seconds.

๐ŸŒฟ Such numbers help us measure quantities more accurately. These numbers are called decimal numbers. This chapter introduces us to the idea of numbers that go beyond the point, that is, numbers written using a decimal point.

๐ŸŸข Meaning of Decimal Numbers

๐Ÿง  A decimal number is a number that has a decimal point and digits after it.

๐Ÿ”น The part before the decimal point shows whole units
๐Ÿ”น The part after the decimal point shows parts of a whole

๐Ÿ“Œ Example
In the number 4.7
๐Ÿ”น 4 represents whole units
๐Ÿ”น 7 represents parts of a unit

๐Ÿ’ก Concept:
Decimals help us represent quantities that lie between two whole numbers.

๐Ÿ”ต Place Value in Decimal Numbers

๐Ÿง  Just like whole numbers, digits in decimal numbers also have place values.

๐Ÿ”น Ones
๐Ÿ”น Tenths
๐Ÿ”น Hundredths
๐Ÿ”น Thousandths

๐Ÿ“Œ Example
In the number 3.456
๐Ÿ”น 4 is in the tenths place
๐Ÿ”น 5 is in the hundredths place
๐Ÿ”น 6 is in the thousandths place

๐Ÿ’ก Concept:
Each place to the right of the decimal point is one-tenth of the previous place.

๐ŸŸข Reading and Writing Decimal Numbers

๐Ÿง  Decimal numbers are read by reading the whole number part first, then saying โ€œpointโ€, followed by each digit after the point.

๐Ÿ“Œ Example
2.35 is read as
Two point three five

โœ๏ธ Note:
Digits after the decimal point are read individually, not as a whole number.

๐Ÿ”ต Writing Decimals from Words

๐Ÿง  To write decimal numbers given in words, identify the place value of each part.

๐Ÿ“Œ Example
Three and five tenths

๐Ÿ”น Three = 3
๐Ÿ”น Five tenths = 0.5
๐Ÿ”น Decimal number = 3.5

๐Ÿ’ก Concept:
The word โ€œtenthsโ€ shows one digit after the decimal point, while โ€œhundredthsโ€ shows two digits.

๐ŸŸก Comparing Decimal Numbers

๐Ÿง  Decimal numbers can be compared just like whole numbers, but with special care.

๐Ÿ”น First compare the whole number part
๐Ÿ”น If equal, compare digits after the decimal point

๐Ÿ“Œ Example
Compare 4.25 and 4.3

๐Ÿ”น Whole number part is same
๐Ÿ”น Compare tenths: 2 < 3
๐Ÿ”น So 4.3 is greater

โœ๏ธ Note:
Write the decimals with the same number of decimal places to compare easily.

๐ŸŸข Ordering Decimal Numbers

๐Ÿง  Ordering means arranging numbers from smallest to greatest or vice versa.

๐Ÿ”น Ascending order: smallest to greatest
๐Ÿ”น Descending order: greatest to smallest

๐Ÿ“Œ Example
Arrange 2.5, 2.35, 2.8

Ascending order
2.35 < 2.5 < 2.8

๐Ÿ”ต Using Zeros in Decimal Numbers

๐Ÿง  Adding zeros after the decimal point does not change the value of a decimal number.

๐Ÿ“Œ Example
2.5 = 2.50 = 2.500

๐Ÿ’ก Concept:
Zeros are often added to make decimals easier to compare or calculate.

๐ŸŸก Decimal Numbers on the Number Line

๐Ÿง  Decimal numbers can be shown clearly on a number line.

๐Ÿ”น Divide the space between two whole numbers into equal parts
๐Ÿ”น Each part represents tenths or hundredths

๐Ÿ“Œ Example
The number 3.4 lies between 3 and 4, closer to 3 than to 4.

โœ๏ธ Note:
The number line helps us visualise the position of decimal numbers.

๐ŸŸข Decimals in Daily Life

๐Ÿง  Decimal numbers are used widely in everyday life.

๐Ÿ”น Money such as 12.50 rupees
๐Ÿ”น Length like 1.75 metres
๐Ÿ”น Weight like 2.3 kilograms
๐Ÿ”น Time like 4.5 seconds

๐Ÿ’ก Concept:
Decimals make measurements more precise and meaningful.

๐Ÿ”ด Common Mistakes to Avoid

๐Ÿ”ด Ignoring place value after the decimal point
๐Ÿ”ด Comparing decimals without aligning decimal points
๐Ÿ”ด Thinking that 2.5 is smaller than 2.35
๐Ÿ”ด Misreading decimal numbers

โœ๏ธ Note:
Always compare decimals by looking at place values step by step.

๐ŸŸข Importance of Learning Decimals

๐Ÿง  Learning decimal numbers helps us:

๐Ÿ”น Measure quantities accurately
๐Ÿ”น Understand money calculations
๐Ÿ”น Read scientific data
๐Ÿ”น Prepare for higher mathematics

This chapter builds a strong foundation for fractions, percentages, and algebra.

๐Ÿ“˜ Summary

๐Ÿ”ต Decimal numbers represent parts of a whole
๐ŸŸข They contain a decimal point
๐ŸŸก Place value extends beyond the decimal point
๐Ÿ”ด Tenths, hundredths, and thousandths show precision
๐Ÿ”ต Decimals can be compared and ordered
๐ŸŸข Zeros after the decimal do not change value
๐ŸŸก Decimals are widely used in daily life

๐Ÿ“ Quick Recap

๐Ÿ“ Quick Recap
๐Ÿ”ต Decimal numbers go beyond whole numbers
๐ŸŸข Decimal point separates whole and fractional parts
๐ŸŸก Place value continues after the point
๐Ÿ”ด Decimals help in accurate measurement
๐Ÿ”ต Decimals are essential in daily life

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TEXTBOOK QUESTIONS

๐Ÿ”ต A TENTH PART

๐Ÿ”’ โ“ Arrange these lengths in increasing order:

(a) 9/10
(b) 1 7/10
(c) 130/10
(d) 13 1/10
(e) 10 5/10
(f) 7 6/10
(g) 6 7/10
(h) 4/10

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Convert all to tenths for easy comparison.
๐Ÿ”ธ 9/10 = 9/10
๐Ÿ”ธ 1 7/10 = 17/10
๐Ÿ”ธ 130/10 = 130/10
๐Ÿ”ธ 13 1/10 = 131/10
๐Ÿ”ธ 10 5/10 = 105/10
๐Ÿ”ธ 7 6/10 = 76/10
๐Ÿ”ธ 6 7/10 = 67/10
๐Ÿ”ธ 4/10 = 4/10

๐Ÿ”น Arrange from smallest to largest (by numerators).

โœ”๏ธ Final:
4/10, 9/10, 1 7/10, 6 7/10, 7 6/10, 10 5/10, 130/10, 13 1/10

๐Ÿ”’ โ“ Arrange the following lengths in increasing order:
4 1/10, 4/10, 41/10, 1/10.

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Write all lengths in tenths.
๐Ÿ”ธ 4 1/10 = 41/10
๐Ÿ”ธ 4/10 = 4/10
๐Ÿ”ธ 41/10 = 41/10
๐Ÿ”ธ 1/10 = 1/10

๐Ÿ”น Compare numerators.

โœ”๏ธ Final:
1/10, 4/10, 4 1/10, 41/10

๐Ÿ”’ โ“ Sonu is measuring some of his body parts. The length of Sonuโ€™s lower arm is 2 7/10 units, and that of his upper arm is 3 6/10 units. What is the total length of his arm?

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Add whole-number parts.
๐Ÿ”ธ 2 + 3 = 5

๐Ÿ”น Add fractional parts.
๐Ÿ”ธ 7/10 + 6/10 = 13/10

๐Ÿ”น Combine whole and fractional parts.
๐Ÿ”ธ 5 + 13/10

๐Ÿ”น Convert improper fraction.
๐Ÿ”ธ 13/10 = 1 + 3/10

๐Ÿ”น Add again.
๐Ÿ”ธ 5 + 1 + 3/10 = 6 3/10

โœ”๏ธ Final:
The total length of Sonuโ€™s arm is 6 3/10 units.

๐Ÿ”’ โ“ The lengths of the body parts of a honeybee are given. Find its total length.

Head: 2 3/10 units
Thorax: 5 4/10 units
Abdomen: 7 5/10 units

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น We are given three lengths written as mixed numbers.
๐Ÿ”น To add them easily, we first add whole parts and tenths parts separately.

๐Ÿ”น Step 1: Add the whole-number parts
๐Ÿ”ธ Head = 2 units
๐Ÿ”ธ Thorax = 5 units
๐Ÿ”ธ Abdomen = 7 units
๐Ÿ”ธ Total whole units = 2 + 5 + 7 = 14

๐Ÿ”น Step 2: Add the tenths
๐Ÿ”ธ 3/10 + 4/10 + 5/10
๐Ÿ”ธ = 12/10

๐Ÿ”น Step 3: Convert extra tenths into units
๐Ÿ”ธ 12/10 means 1 whole unit and 2/10
๐Ÿ”ธ So, 12/10 = 1 + 2/10

๐Ÿ”น Step 4: Add everything together
๐Ÿ”ธ 14 + 1 + 2/10 = 15 2/10

โœ”๏ธ Final:
The total length of the honeybee is 15 2/10 units.

๐Ÿ”’ โ“ The length of Shylajaโ€™s hand is 12 4/10 units, and her palm is 6 7/10 units, as shown in the picture. What is the length of the longest (middle) finger?

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น The hand length includes the palm and the finger.
๐Ÿ”น To find only the finger length, we subtract the palm length from the total hand length.

๐Ÿ”น Step 1: Write the subtraction clearly
๐Ÿ”ธ (12 4/10) โˆ’ (6 7/10)

๐Ÿ”น Step 2: Separate whole numbers and tenths
๐Ÿ”ธ (12 โˆ’ 6) + (4/10 โˆ’ 7/10)

๐Ÿ”น Step 3: Subtract the whole numbers
๐Ÿ”ธ 12 โˆ’ 6 = 6

๐Ÿ”น Step 4: Observe the tenths carefully
๐Ÿ”ธ We cannot subtract 7/10 from 4/10
๐Ÿ”ธ So, we regroup 1 unit from 6

๐Ÿ”น Step 5: Regroup 1 unit as tenths
๐Ÿ”ธ 1 unit = 10/10
๐Ÿ”ธ 6 becomes 5 + 10/10

๐Ÿ”น Step 6: Subtract the tenths
๐Ÿ”ธ 10/10 โˆ’ 3/10 = 7/10

๐Ÿ”น Step 7: Combine the result
๐Ÿ”ธ 5 + 7/10 = 5 7/10

๐Ÿ’ก Concept:
Regrouping helps when the fractional part of the minuend is smaller than the fractional part of the subtrahend.

โœ”๏ธ Final:
The length of the longest (middle) finger is 5 7/10 units.

๐Ÿ”’ โ“ Try computing the difference by converting both lengths to tenths.
A Celestial Pearl Danioโ€™s length is 2 4/10 cm, and the length of a Philippine Goby is 9/10 cm. What is the difference in their lengths?

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น To find the difference, both lengths should be written in the same form.
๐Ÿ”น We convert both lengths into tenths.

๐Ÿ”น Step 1: Convert mixed number to tenths
๐Ÿ”ธ 2 4/10 = 24/10

๐Ÿ”น Step 2: Write the second length in tenths
๐Ÿ”ธ 9/10 = 9/10

๐Ÿ”น Step 3: Subtract the lengths
๐Ÿ”ธ 24/10 โˆ’ 9/10 = 15/10

๐Ÿ”น Step 4: Convert back to mixed number
๐Ÿ”ธ 15/10 = 1 5/10

โœ”๏ธ Final:
The difference in their lengths is 1 5/10 cm.

๐Ÿ”’ โ“ How big are these fish compared to your finger?

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น The lengths of both fish are less than 3 cm.
๐Ÿ”น A finger of a student is usually longer than 5 cm.

๐Ÿ”น Therefore, both fish are shorter than a finger.

โœ”๏ธ Final:
Both fish are shorter than a finger.

๐Ÿ”’ โ“ Observe the given sequences of numbers. Identify the change after each term and extend the pattern:

๐Ÿ”’ โ“ (a) 4, 4 3/10, 4 6/10, ___, ___, ___

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น Write the numbers in tenths.
๐Ÿ”ธ 4 = 4 0/10

๐Ÿ”น Find the change between terms.
๐Ÿ”ธ 4 0/10 โ†’ 4 3/10 = +3/10
๐Ÿ”ธ 4 3/10 โ†’ 4 6/10 = +3/10

๐Ÿ”น The pattern increases by 3/10 each time.

โœ”๏ธ Final:
4 9/10, 5 2/10, 5 5/10

๐Ÿ”’ โ“ (b) 8 2/10, 8 7/10, 9 2/10, ___, ___, ___

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น Find the difference between terms.
๐Ÿ”ธ 8 2/10 โ†’ 8 7/10 = +5/10
๐Ÿ”ธ 8 7/10 โ†’ 9 2/10 = +5/10

๐Ÿ”น The pattern increases by 5/10.

โœ”๏ธ Final:
9 7/10, 10 2/10, 10 7/10

๐Ÿ”’ โ“ (c) 7 6/10, 8 7/10, ___, ___, ___

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น Convert to tenths.
๐Ÿ”ธ 7 6/10 = 76/10
๐Ÿ”ธ 8 7/10 = 87/10

๐Ÿ”น Find the change.
๐Ÿ”ธ 87/10 โˆ’ 76/10 = 11/10 = 1 1/10

๐Ÿ”น The pattern increases by 1 1/10.

โœ”๏ธ Final:
9 8/10, 10 9/10, 12 0/10

๐Ÿ”’ โ“ (d) 5 7/10, 5 3/10, ___, ___, ___

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น Observe the change.
๐Ÿ”ธ 5 7/10 โ†’ 5 3/10 = โˆ’4/10

๐Ÿ”น The pattern decreases by 4/10.

โœ”๏ธ Final:
4 9/10, 4 5/10, 4 1/10

๐Ÿ”’ โ“ (e) 13 5/10, 13, 12 5/10, ___, ___, ___

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น Write all terms in tenths.
๐Ÿ”ธ 13 5/10 โ†’ 13 0/10 โ†’ 12 5/10

๐Ÿ”น Each step decreases by 5/10.

โœ”๏ธ Final:
12 0/10, 11 5/10, 11 0/10

๐Ÿ”’ โ“ (f) 11 5/10, 10 4/10, 9 3/10, ___, ___, ___

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น Find the difference.
๐Ÿ”ธ 11 5/10 โ†’ 10 4/10 = โˆ’1 1/10
๐Ÿ”ธ 10 4/10 โ†’ 9 3/10 = โˆ’1 1/10

๐Ÿ”น The pattern decreases by 1 1/10 each time.

โœ”๏ธ Final:
8 2/10, 7 1/10, 6 0/10

๐Ÿ”ต A HUNDREDTH PART

๐Ÿ”’ โ“ Figure it Out โ€“ Find the sums and differences

๐Ÿ”’ โ“ (a) 3/10 + 3 4/100

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น First, both numbers should be written with the same denominator.
๐Ÿ”น 3/10 can be written in hundredths.

๐Ÿ”น Step 1: Convert 3/10 into hundredths
๐Ÿ”ธ 3/10 = 30/100

๐Ÿ”น Step 2: Write both numbers clearly
๐Ÿ”ธ 30/100 + 3 4/100

๐Ÿ”น Step 3: Add fractional parts
๐Ÿ”ธ 30/100 + 4/100 = 34/100

๐Ÿ”น Step 4: Add the whole number
๐Ÿ”ธ 3 + 34/100

โœ”๏ธ Final:
3 34/100

๐Ÿ”’ โ“ (b) 9 5/10 7/100 + 2 1/10 3/100

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น Add whole parts, tenths, and hundredths separately.

๐Ÿ”น Step 1: Add whole numbers
๐Ÿ”ธ 9 + 2 = 11

๐Ÿ”น Step 2: Add tenths
๐Ÿ”ธ 5/10 + 1/10 = 6/10

๐Ÿ”น Step 3: Add hundredths
๐Ÿ”ธ 7/100 + 3/100 = 10/100

๐Ÿ”น Step 4: Convert 10/100 into tenths
๐Ÿ”ธ 10/100 = 1/10

๐Ÿ”น Step 5: Add tenths again
๐Ÿ”ธ 6/10 + 1/10 = 7/10

๐Ÿ”น Step 6: Combine all parts
๐Ÿ”ธ 11 7/10

โœ”๏ธ Final:
11 7/10

๐Ÿ”’ โ“ (c) 15 6/10 4/100 + 14 3/10 6/100

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น Add each part carefully.

๐Ÿ”น Step 1: Add whole numbers
๐Ÿ”ธ 15 + 14 = 29

๐Ÿ”น Step 2: Add tenths
๐Ÿ”ธ 6/10 + 3/10 = 9/10

๐Ÿ”น Step 3: Add hundredths
๐Ÿ”ธ 4/100 + 6/100 = 10/100

๐Ÿ”น Step 4: Convert 10/100
๐Ÿ”ธ 10/100 = 1/10

๐Ÿ”น Step 5: Add tenths again
๐Ÿ”ธ 9/10 + 1/10 = 10/10 = 1

๐Ÿ”น Step 6: Add to whole number
๐Ÿ”ธ 29 + 1 = 30

โœ”๏ธ Final:
30

๐Ÿ”’ โ“ (d) 7 7/100 โˆ’ 4 4/100

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น Subtract whole numbers and hundredths separately.

๐Ÿ”น Step 1: Subtract whole numbers
๐Ÿ”ธ 7 โˆ’ 4 = 3

๐Ÿ”น Step 2: Subtract hundredths
๐Ÿ”ธ 7/100 โˆ’ 4/100 = 3/100

๐Ÿ”น Step 3: Combine
๐Ÿ”ธ 3 3/100

โœ”๏ธ Final:
3 3/100

๐Ÿ”’ โ“ (e) 8 6/100 โˆ’ 5 3/100

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น Step 1: Subtract whole numbers
๐Ÿ”ธ 8 โˆ’ 5 = 3

๐Ÿ”น Step 2: Subtract hundredths
๐Ÿ”ธ 6/100 โˆ’ 3/100 = 3/100

๐Ÿ”น Step 3: Combine
๐Ÿ”ธ 3 3/100

โœ”๏ธ Final:
3 3/100

๐Ÿ”’ โ“ (f) 12 6/100 2/100 โˆ’ 9/10 9/100

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น Convert everything into hundredths to avoid confusion.

๐Ÿ”น Step 1: Convert tenths to hundredths
๐Ÿ”ธ 9/10 = 90/100

๐Ÿ”น Step 2: Write numbers clearly
๐Ÿ”ธ 12 8/100 โˆ’ 9 90/100

๐Ÿ”น Step 3: Regroup 1 whole unit
๐Ÿ”ธ 12 = 11 + 100/100

๐Ÿ”น Step 4: Subtract hundredths
๐Ÿ”ธ 108/100 โˆ’ 90/100 = 18/100

๐Ÿ”น Step 5: Subtract whole numbers
๐Ÿ”ธ 11 โˆ’ 9 = 2

๐Ÿ”น Step 6: Combine
๐Ÿ”ธ 2 18/100

โœ”๏ธ Final:
2 18/100

๐Ÿ”ต ADDITION AND SUBTRACTION OF DECIMALS

๐Ÿ”’ โ“ 1. Find the sums

๐Ÿ”’ โ“ (a) 5.3 + 2.6

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น Write decimals one below the other, aligning the decimal points.
๐Ÿ”ธ 5.3
๐Ÿ”ธ 2.6

๐Ÿ”น Add tenths first.
๐Ÿ”ธ 3 + 6 = 9

๐Ÿ”น Add whole numbers.
๐Ÿ”ธ 5 + 2 = 7

โœ”๏ธ Final:
7.9

๐Ÿ”’ โ“ (b) 18 + 8.8

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Write 18 as 18.0 to match decimal places.
๐Ÿ”ธ 18.0
๐Ÿ”ธ 8.8

๐Ÿ”น Add tenths and whole numbers.

โœ”๏ธ Final:
26.8

๐Ÿ”’ โ“ (c) 2.15 + 5.26

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Align decimal points carefully.
๐Ÿ”น Add hundredths, then tenths, then whole numbers.

๐Ÿ”ธ 0.15 + 0.26 = 0.41
๐Ÿ”ธ 2 + 5 = 7

โœ”๏ธ Final:
7.41

๐Ÿ”’ โ“ (d) 9.01 + 9.10

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Align decimals.
๐Ÿ”น Add hundredths and tenths first.

๐Ÿ”ธ 0.01 + 0.10 = 0.11
๐Ÿ”ธ 9 + 9 = 18

โœ”๏ธ Final:
18.11

๐Ÿ”’ โ“ (e) 29.19 + 9.91

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Add hundredths.
๐Ÿ”ธ 0.19 + 0.91 = 1.10

๐Ÿ”น Regroup 1 whole.

๐Ÿ”ธ 29 + 9 + 1 = 39

โœ”๏ธ Final:
39.10

๐Ÿ”’ โ“ (f) 0.934 + 0.6

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Write 0.6 as 0.600.
๐Ÿ”น Add thousandths, hundredths, tenths.

โœ”๏ธ Final:
1.534

๐Ÿ”’ โ“ (g) 0.75 + 0.03

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Add hundredths.

โœ”๏ธ Final:
0.78

๐Ÿ”’ โ“ (h) 6.236 + 0.487

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Add thousandths carefully.
๐Ÿ”น Regroup where needed.

โœ”๏ธ Final:
6.723

๐Ÿ”’ โ“ 2. Find the differences

๐Ÿ”’ โ“ (a) 5.6 โˆ’ 2.3

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Subtract tenths, then whole numbers.

โœ”๏ธ Final:
3.3

๐Ÿ”’ โ“ (b) 18 โˆ’ 8.8

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Write 18 as 18.0.
๐Ÿ”น Subtract tenths carefully.

โœ”๏ธ Final:
9.2

๐Ÿ”’ โ“ (c) 10.4 โˆ’ 4.5

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Regroup 1 unit if needed.

โœ”๏ธ Final:
5.9

๐Ÿ”’ โ“ (d) 17 โˆ’ 16.198

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Write 17 as 17.000.
๐Ÿ”น Regroup across decimal places.

โœ”๏ธ Final:
0.802

๐Ÿ”’ โ“ (e) 17 โˆ’ 0.05

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Write 17 as 17.00.

โœ”๏ธ Final:
16.95

๐Ÿ”’ โ“ (f) 34.505 โˆ’ 18.1

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Write 18.1 as 18.100.
๐Ÿ”น Subtract step-by-step.

โœ”๏ธ Final:
16.405

๐Ÿ”’ โ“ (g) 9.9 โˆ’ 9.09

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Write 9.9 as 9.90.
๐Ÿ”น Subtract hundredths.

โœ”๏ธ Final:
0.81

๐Ÿ”’ โ“ (h) 6.236 โˆ’ 0.487

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Subtract thousandths with regrouping.

โœ”๏ธ Final:
5.749

๐Ÿ”ต FIGURE IT OUT ?

๐Ÿ”’ โ“ 1. Convert the following fractions into decimals:

๐Ÿ”’ โ“ (a) 5/100

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น The denominator is 100, so the fraction represents hundredths.
๐Ÿ”น Move the decimal point two places to the left.

๐Ÿ”ธ 5/100 = 0.05

โœ”๏ธ Final:
0.05

๐Ÿ”’ โ“ (b) 16/1000

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น The denominator is 1000, so the fraction represents thousandths.
๐Ÿ”น Move the decimal point three places to the left.

๐Ÿ”ธ 16/1000 = 0.016

โœ”๏ธ Final:
0.016

๐Ÿ”’ โ“ (c) 12/10

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น The denominator is 10, so the fraction represents tenths.
๐Ÿ”น Move the decimal point one place to the left.

๐Ÿ”ธ 12/10 = 1.2

โœ”๏ธ Final:
1.2

๐Ÿ”’ โ“ (d) 254/1000

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Denominator 1000 means thousandths.
๐Ÿ”น Move the decimal point three places to the left.

๐Ÿ”ธ 254/1000 = 0.254

โœ”๏ธ Final:
0.254

๐Ÿ”’ โ“ 2. Convert the following decimals into a sum of tenths, hundredths and thousandths:

๐Ÿ”’ โ“ (a) 0.34

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น The digit 3 is in the tenths place.
๐Ÿ”น The digit 4 is in the hundredths place.

๐Ÿ”ธ 0.34 = 3/10 + 4/100

โœ”๏ธ Final:
3/10 + 4/100

๐Ÿ”’ โ“ (b) 1.02

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น 1 is the whole number.
๐Ÿ”น 0 tenths and 2 hundredths.

๐Ÿ”ธ 1.02 = 1 + 2/100

โœ”๏ธ Final:
1 + 2/100

๐Ÿ”’ โ“ (c) 0.8

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น 8 is in the tenths place.

๐Ÿ”ธ 0.8 = 8/10

โœ”๏ธ Final:
8/10

๐Ÿ”’ โ“ (d) 0.362

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น 3 tenths, 6 hundredths, 2 thousandths.

๐Ÿ”ธ 0.362 = 3/10 + 6/100 + 2/1000

โœ”๏ธ Final:
3/10 + 6/100 + 2/1000

๐Ÿ”’ โ“ 3. What decimal number does each letter represent in the number line below?

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):
๐Ÿ”น The arrow a is on the tick just after 6.44, so
๐Ÿ”ธ a = 6.46

๐Ÿ”น The arrows c and b are the first two ticks to the right of 6.5, so
๐Ÿ”ธ c = 6.52
๐Ÿ”ธ b = 6.54

โœ”๏ธ Final (Correct):
๐Ÿ“Œ โœ… a = 6.46, c = 6.52, b = 6.54

๐Ÿ”’ โ“ 4. Arrange the following quantities in descending order:

๐Ÿ”’ โ“ (a) 11.01, 1.011, 1.101, 11.10, 1.01

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Compare whole numbers first.

โœ”๏ธ Final:
11.10, 11.01, 1.101, 1.011, 1.01

๐Ÿ”’ โ“ (b) 2.567, 2.675, 2.768, 2.499, 2.698

๐Ÿ“Œ โœ… Answer:

โœ”๏ธ Final:
2.768, 2.698, 2.675, 2.567, 2.499

๐Ÿ”’ โ“ (c) 4.678 g, 4.595 g, 4.600 g, 4.656 g, 4.666 g

๐Ÿ“Œ โœ… Answer:

โœ”๏ธ Final:
4.678 g, 4.666 g, 4.656 g, 4.600 g, 4.595 g

๐Ÿ”’ โ“ (d) 33.13 m, 33.31 m, 33.133 m, 33.331 m, 33.313 m

๐Ÿ“Œ โœ… Answer:

โœ”๏ธ Final:
33.331 m, 33.313 m, 33.31 m, 33.133 m, 33.13 m

๐Ÿ”’ โ“ 5. Using the digits 1, 4, 0, 8, and 6 make:

๐Ÿ”’ โ“ (a) the decimal number closest to 30

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น We must use only digits 1,4,0,8,6 exactly once.
๐Ÿ”น To be closest to 30, the nearest possible whole-part using these digits is 40 (because we cannot form 29 or 30 without digit 2 or 3).
๐Ÿ”น To make it closest, keep the decimal part as small as possible while using remaining digits.

โœ”๏ธ Final (Correct):
๐Ÿ“Œ โœ… 40.168

๐Ÿ”’ โ“ (b) the smallest possible decimal number between 100 and 1000

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น The smallest number is formed by keeping the hundreds digit as small as possible.

โœ”๏ธ Final:
104.68

๐Ÿ”’ โ“ 6. Will a decimal number with more digits be greater than a decimal number with fewer digits?

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น No.
๐Ÿ”น The value of a decimal depends on its place value, not the number of digits.

โœ”๏ธ Final:
A decimal with more digits is not always greater.

๐Ÿ”’ โ“ 7. Mahi purchases 0.25 kg of beans, 0.3 kg of carrots, 0.5 kg of potatoes, 0.2 kg of capsicums, and 0.05 kg of ginger. Calculate the total weight.

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Add all weights.

๐Ÿ”ธ 0.25 + 0.30 + 0.50 + 0.20 + 0.05
๐Ÿ”ธ = 1.30

โœ”๏ธ Final:
1.3 kg

๐Ÿ”’ โ“ 8. Pinto supplies 3.79 L, 4.2 L, and 4.25 L of milk in the first three days. In 6 days, he supplies 25 L of milk. Find the quantity supplied in the last three days.

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Milk supplied in first three days:

๐Ÿ”ธ 3.79 + 4.20 + 4.25 = 12.24

๐Ÿ”น Milk supplied in last three days:

๐Ÿ”ธ 25 โˆ’ 12.24 = 12.76

โœ”๏ธ Final:
12.76 L

๐Ÿ”’ โ“ 9. Tinku weighed 35.75 kg in January and 34.50 kg in February. Has he gained or lost weight? How much is the change?

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น January weight = 35.75 kg
๐Ÿ”น February weight = 34.50 kg

๐Ÿ”น To find the change, subtract February weight from January weight.

๐Ÿ”ธ 35.75 โˆ’ 34.50 = 1.25

๐Ÿ”น Since the weight has decreased, Tinku has lost weight.

โœ”๏ธ Final:
Tinku has lost 1.25 kg.

๐Ÿ”’ โ“ Q10. Extend the pattern:
5.5, 6.4, 6.39, 7.29, 7.28, 6.18, 6.17, ___, ___

๐Ÿ“Œ โœ… Answer (Teacher-like, step-by-step explanation):

๐Ÿ”น First, observe that the numbers come in pairs.

๐Ÿ”น Write the numbers pair-wise to see the pattern clearly:

๐Ÿ”ธ (6.4, 6.39)
๐Ÿ”ธ (7.29, 7.28)
๐Ÿ”ธ (6.18, 6.17)

๐Ÿ”น In each pair, the second number is 0.01 less than the first.

๐Ÿ”น Now focus only on the first numbers of each pair:

๐Ÿ”ธ 6.4
๐Ÿ”ธ 7.29
๐Ÿ”ธ 6.18

๐Ÿ”น Notice the change:

  • 6.4 โ†’ 7.29 (+0.89)
  • 7.29 โ†’ 6.18 (โˆ’1.11)

๐Ÿ”น This increase and decrease happens alternately.

๐Ÿ”น Since the last first-number was 6.18, the next first-number will be:

๐Ÿ”ธ 6.18 โˆ’ 1.11 = 5.07

๐Ÿ”น Following the pair rule, the next number will be:

๐Ÿ”ธ 5.07 โˆ’ 0.01 = 5.06

โœ”๏ธ Final:
๐Ÿ“Œ โœ… 5.07, 5.06

๐Ÿ”’ โ“ 11. How many millimeters make 1 kilometer?

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น 1 kilometer = 1000 meters
๐Ÿ”น 1 meter = 1000 millimeters

๐Ÿ”น Multiply:

๐Ÿ”ธ 1000 ร— 1000 = 1,000,000

โœ”๏ธ Final:
1 kilometer = 1,000,000 millimeters

๐Ÿ”’ โ“ 12. Indian Railways offers optional travel insurance costing 45 paise per passenger. If 1 lakh people opt for insurance in a day, what is the total insurance fee paid?

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น Cost per passenger = 45 paise
๐Ÿ”น 1 lakh people = 100,000 people

๐Ÿ”น Total cost in paise:

๐Ÿ”ธ 100,000 ร— 45 = 4,500,000 paise

๐Ÿ”น Convert paise to rupees
๐Ÿ”ธ 100 paise = 1 rupee

๐Ÿ”ธ 4,500,000 รท 100 = 45,000

โœ”๏ธ Final:
The total insurance fee paid is โ‚น45,000.

๐Ÿ”’ โ“ 13. Which is greater?

๐Ÿ”’ โ“ (a) 10/1000 or 1/10 ?

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Convert both to decimals.

๐Ÿ”ธ 10/1000 = 0.01
๐Ÿ”ธ 1/10 = 0.1

โœ”๏ธ Final:
1/10 is greater.

๐Ÿ”’ โ“ (b) One-hundredth or 90 thousandths?

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น One-hundredth = 1/100 = 0.01
๐Ÿ”น 90 thousandths = 90/1000 = 0.09

โœ”๏ธ Final:
90 thousandths is greater.

๐Ÿ”’ โ“ (c) One-thousandth or 90 hundredths?

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น One-thousandth = 1/1000 = 0.001
๐Ÿ”น 90 hundredths = 90/100 = 0.90

โœ”๏ธ Final:
90 hundredths is greater.

๐Ÿ”’ โ“ 14. Write the decimal forms of the quantities mentioned:

๐Ÿ”’ โ“ (a) 87 ones, 5 tenths and 60 hundredths

๐Ÿ“Œ โœ… Answer:

โœ”๏ธ Final:
88.10

๐Ÿ”’ โ“ (b) 12 tens and 12 tenths

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น 12 tens = 120
๐Ÿ”น 12 tenths = 1.2

โœ”๏ธ Final:
121.2

๐Ÿ”’ โ“ (c) 10 tens, 10 ones, 10 tenths, and 10 hundredths

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น 10 tens = 100
๐Ÿ”น 10 ones = 10
๐Ÿ”น 10 tenths = 1
๐Ÿ”น 10 hundredths = 0.10

โœ”๏ธ Final:
111.10

๐Ÿ”’ โ“ (d) 25 tens, 25 ones, 25 tenths, and 25 hundredths

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น 25 tens = 250
๐Ÿ”น 25 ones = 25
๐Ÿ”น 25 tenths = 2.5
๐Ÿ”น 25 hundredths = 0.25

โœ”๏ธ Final:
277.75

๐Ÿ”’ โ“ 15. Using each digit 0โ€“9 not more than once, fill the boxes so that the sum is closest to 10.5

๐Ÿ“Œ โœ… Answer (Teacher-like explanation):

๐Ÿ”น One possible arrangement close to 10.5 is:

๐Ÿ”ธ 5.26
๐Ÿ”ธ 5.24

๐Ÿ”น Sum = 10.50

โœ”๏ธ Final:
A correct arrangement gives a sum of 10.5.

๐Ÿ”’ โ“ 16. Write the following fractions in decimal form:

๐Ÿ”’ โ“ (a) 1/2

๐Ÿ“Œ โœ… Answer:
0.5

๐Ÿ”’ โ“ (b) 3/2

๐Ÿ“Œ โœ… Answer:
1.5

๐Ÿ”’ โ“ (c) 1/4

๐Ÿ“Œ โœ… Answer:
0.25

๐Ÿ”’ โ“ (d) 3/4

๐Ÿ“Œ โœ… Answer:
0.75

๐Ÿ”’ โ“ (e) 1/5

๐Ÿ“Œ โœ… Answer:
0.2

๐Ÿ”’ โ“ (f) 4/5

๐Ÿ“Œ โœ… Answer:
0.8

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OTHER IMPORTANT QUESTIONS

( MODEL QUESTION PAPER )

ESPECIALLY MADE FOR THIS LESSON ONLY

๐Ÿ”ต Section A โ€“ Very Short Answer (1 ร— 6 = 6 marks)

๐Ÿ”’ โ“ Question 1
What is a decimal number?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น A decimal number is a number that has a decimal point
๐Ÿ”น It shows parts of a whole

๐Ÿ”’ โ“ Question 2
Write one decimal number between 2 and 3.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น One decimal number between 2 and 3 is 2.5

๐Ÿ”’ โ“ Question 3
How many tenths make one whole?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Ten tenths make one whole

๐Ÿ”’ โ“ Question 4
What is the place value of 4 in 3.47?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น The digit 4 is in the tenths place

๐Ÿ”’ โ“ Question 5
True or False: 2.5 = 2.50

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น True

๐Ÿ”’ โ“ Question 6
Which is greater: 0.6 or 0.56?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Write both with same decimal places: 0.60 and 0.56
๐Ÿ”น 0.60 is greater

๐ŸŸข Section B โ€“ Short Answer I (2 ร— 6 = 12 marks)

๐Ÿ”’ โ“ Question 7
Write the place value of each digit in 4.305.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น 4 is in the ones place
๐Ÿ”น 3 is in the tenths place
๐Ÿ”น 0 is in the hundredths place
๐Ÿ”น 5 is in the thousandths place

๐Ÿ”’ โ“ Question 8
Write 3.7 in words.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Three point seven

๐Ÿ”’ โ“ Question 9
Compare 5.2 and 5.18.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Write both with same decimal places: 5.20 and 5.18
๐Ÿ”น 5.20 is greater
๐Ÿ”น So 5.2 > 5.18

๐Ÿ”’ โ“ Question 10
Write any two decimal numbers between 1.2 and 1.3.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น 1.21
๐Ÿ”น 1.25

๐Ÿ”’ โ“ Question 11
Why are zeros added after a decimal number?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Zeros do not change the value of a decimal number
๐Ÿ”น They help in comparison and calculation

๐Ÿ”’ โ“ Question 12
Write the decimal form of five tenths.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Five tenths = 0.5

๐ŸŸก Section C โ€“ Short Answer II (3 ร— 10 = 30 marks)

๐Ÿ”’ โ“ Question 13
Write the number name of 2.406.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Two point four zero six

๐Ÿ”’ โ“ Question 14
Compare 3.75 and 3.705 using place value.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Write both with same decimal places: 3.750 and 3.705
๐Ÿ”น Compare hundredths place: 5 > 0
๐Ÿ”น So 3.75 is greater

๐Ÿ”’ โ“ Question 15
Write three decimal numbers between 4.2 and 4.3.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น 4.21
๐Ÿ”น 4.25
๐Ÿ”น 4.29

๐Ÿ”’ โ“ Question 16
Explain the meaning of tenths and hundredths.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Tenths represent one part out of ten equal parts
๐Ÿ”น Hundredths represent one part out of one hundred equal parts

๐Ÿ”’ โ“ Question 17
Arrange 1.45, 1.5, and 1.405 in ascending order.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Write with same decimal places: 1.450, 1.500, 1.405
๐Ÿ”น Ascending order
๐Ÿ”น 1.405 < 1.45 < 1.5

๐Ÿ”’ โ“ Question 18
Write the expanded form of 3.204.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น 3 + 2/10 + 0/100 + 4/1000

๐Ÿ”’ โ“ Question 19
Explain how decimal numbers are useful in daily life.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Used in money
๐Ÿ”น Used in measurement of length and weight
๐Ÿ”น Used in time calculation

๐Ÿ”’ โ“ Question 20
Write two decimal numbers equal to 6.3.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น 6.30
๐Ÿ”น 6.300

๐Ÿ”’ โ“ Question 21
What is the successor of 2.99?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น One successor of 2.99 is 3.00

๐Ÿ”’ โ“ Question 22
Explain how decimals are shown on a number line.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Divide the space between two whole numbers into equal parts
๐Ÿ”น Each part represents tenths or hundredths

๐Ÿ”ด Section D โ€“ Long Answer (4 ร— 8 = 32 marks)

๐Ÿ”’ โ“ Question 23
Explain place value in decimal numbers with an example.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Digits to the right of the decimal point have place values like tenths and hundredths
๐Ÿ”น Example: In 4.36
๐Ÿ”น 3 is in the tenths place
๐Ÿ”น 6 is in the hundredths place

๐Ÿ”’ โ“ Question 24
Compare 7.08 and 7.8 and explain the steps.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Write both with same decimal places: 7.08 and 7.80
๐Ÿ”น Compare tenths place: 0 < 8
๐Ÿ”น So 7.8 is greater

๐Ÿ”’ โ“ Question 25
Write five decimal numbers between 2.4 and 2.5.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น 2.41
๐Ÿ”น 2.42
๐Ÿ”น 2.43
๐Ÿ”น 2.44
๐Ÿ”น 2.45

๐Ÿ”’ โ“ Question 26
Explain the use of zeros in decimal numbers with examples.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Zeros added after the decimal do not change value
๐Ÿ”น Example: 5.6 = 5.60 = 5.600

๐Ÿ”’ โ“ Question 27
Show 3.6 on the number line (explain in words).

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Take the interval between 3 and 4
๐Ÿ”น Divide it into ten equal parts
๐Ÿ”น The sixth part from 3 represents 3.6

๐Ÿ”’ โ“ Question 28
Arrange 4.125, 4.12, and 4.205 in descending order.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Write with same decimal places: 4.125, 4.120, 4.205
๐Ÿ”น Descending order
๐Ÿ”น 4.205 > 4.125 > 4.12

๐Ÿ”’ โ“ Question 29
Explain any four common mistakes while working with decimal numbers.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Ignoring place value
๐Ÿ”น Comparing without aligning decimal points
๐Ÿ”น Misreading decimals
๐Ÿ”น Thinking 2.5 is smaller than 2.35

๐Ÿ”’ โ“ Question 30
Explain the importance of decimal numbers in daily life.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Used in money transactions
๐Ÿ”น Used in measurements
๐Ÿ”น Used in science and data
๐Ÿ”น Helps in accurate calculation

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