Class 7, Maths

Class 7 : Maths โ€“ Lesson 1. Large Numbers Around Us

EXPLANATION AND ANALYSIS

๐Ÿ”ต Introduction: Large Numbers in Everyday Life

๐Ÿง  In our daily activities, we usually deal with small numbers such as the number of books, students, or money spent on simple items. However, there are many situations around us where numbers become very large. Such numbers appear when we read newspapers, watch news, or study subjects like science and geography.

๐ŸŒฟ Examples from daily life
๐Ÿ”ต Population of a country is counted in crores
๐ŸŸข Distance between planets is measured in thousands or lakhs of kilometres
๐ŸŸก Government budgets involve very large numbers
๐Ÿ”ด Digital data is measured in gigabytes and terabytes

โžก๏ธ To understand these facts clearly, we must learn how to read, write, compare, and estimate large numbers correctly. This chapter introduces these ideas.

๐ŸŸข Place Value: The Basis of Large Numbers

๐Ÿง  Every digit in a number has a value depending on its position. This is called the place value of the digit.

๐Ÿ“Œ Example
In the number 4,36,728, the digit 3 represents 30,000.

๐Ÿ’ก Concept:
Each place to the left has a value ten times greater than the place to its right.

๐Ÿ”ต Indian Place Value System

๐Ÿง  In India, we follow the Indian place value system.

๐Ÿ”ต Ones
๐ŸŸข Tens
๐ŸŸก Hundreds
๐Ÿ”ด Thousands
๐Ÿ”ต Lakhs
๐ŸŸข Crores

๐Ÿ“Œ Example
The number 6,48,25,309 is read as
Six crore forty-eight lakh twenty-five thousand three hundred nine

โœ๏ธ Note:
In the Indian system, commas are placed after the first three digits from the right and then after every two digits.

๐ŸŸข International Place Value System

๐ŸŒ Many other countries use the International place value system.

๐Ÿ”ต Ones
๐ŸŸข Tens
๐ŸŸก Hundreds
๐Ÿ”ด Thousands
๐Ÿ”ต Millions
๐ŸŸข Billions

๐Ÿ“Œ Example
The number 64,825,309 is read as
Sixty-four million eight hundred twenty-five thousand three hundred nine

๐Ÿ’ก Concept:
Indian system uses lakh and crore, while International system uses million and billion.

๐ŸŸก Reading Large Numbers

๐Ÿง  To read large numbers correctly, we should follow a fixed method.

๐Ÿ”ต Place commas correctly
๐ŸŸข Start reading from the leftmost group
๐ŸŸก Use correct place value names

๐Ÿ“Œ Example
5,03,07,418 is read as
Five crore three lakh seven thousand four hundred eighteen

๐Ÿ”ด Common mistake:
Reading digits one by one instead of using place values.

๐Ÿ”ต Writing Large Numbers in Numerals

๐Ÿง  While writing numbers given in words, it is important to identify place value words like thousand, lakh, and crore.

๐Ÿ“Œ Example
Seven crore four lakh two thousand sixty-five
7,04,02,065

โœ๏ธ Note:
Zeros are very important in large numbers. Missing a zero changes the value of the number.

๐ŸŸข Comparing Large Numbers

๐Ÿง  Large numbers can be compared easily by following a fixed order.

๐Ÿ”ต Step 1: Compare the number of digits
๐ŸŸข Step 2: If digits are equal, compare digits from the left
๐ŸŸก Step 3: The number with the greater digit is larger

๐Ÿ“Œ Example
Compare 8,34,912 and 8,29,745
Both have six digits
At the ten-thousands place, 3 is greater than 2
So 8,34,912 is greater

๐ŸŸก Ordering Large Numbers

๐Ÿง  Ordering means arranging numbers in a particular sequence.

๐Ÿ”ต Ascending order means smallest to greatest
๐ŸŸข Descending order means greatest to smallest

๐Ÿ“Œ Example
2,84,679, 2,96,540, 3,10,428 in ascending order
2,84,679 < 2,96,540 < 3,10,428

๐Ÿ”ต Estimation and Rounding Off

๐Ÿง  Estimation gives an approximate value of a number when an exact value is not required.

๐Ÿ”ต Look at the digit to the right
๐ŸŸข If it is less than 5, round down
๐ŸŸก If it is 5 or more, round up

๐Ÿ“Œ Example
Round 6,72,418 to the nearest thousand
The hundreds digit is 4
The rounded value is 6,72,000

๐Ÿ’ก Concept:
Estimation makes calculations quicker and easier.

๐ŸŸข Use of Large Numbers in Daily Life

๐ŸŒฟ Large numbers are used in many fields.

๐Ÿ”ต Population studies
๐ŸŸข Space science
๐ŸŸก Banking and finance
๐Ÿ”ด Government planning
๐Ÿ”ต Digital storage

๐Ÿ“Œ Example
The distance between Earth and the Moon is about 3,84,400 kilometres.

๐Ÿ”ด Common Errors to Avoid

๐Ÿ”ด Wrong placement of commas
๐Ÿ”ด Mixing Indian and International systems
๐Ÿ”ด Forgetting zeros
๐Ÿ”ด Incorrect reading of place values

โœ๏ธ Note:
Always recheck comma placement before reading or writing a number.

๐ŸŸข Importance of Learning Large Numbers

๐Ÿง  Understanding large numbers helps us interpret real-world data correctly.

๐Ÿ”ต Builds strong number sense
๐ŸŸข Helps in science and geography
๐ŸŸก Useful for higher mathematics
๐Ÿ”ด Important for everyday understanding

๐Ÿ“˜ Summary

๐Ÿ”ต Large numbers help us describe very big quantities
๐ŸŸข Place value gives meaning to each digit
๐ŸŸก Indian and International systems are different
๐Ÿ”ด Correct reading and writing depend on comma placement
๐Ÿ”ต Numbers can be compared and ordered easily
๐ŸŸข Estimation gives approximate values
๐ŸŸก Large numbers are used widely in daily life

๐Ÿ“ Quick Recap

๐Ÿ“ Quick Recap
๐Ÿ”ต Large numbers represent huge quantities
๐ŸŸข Place value decides digit value
๐ŸŸก Indian system uses lakh and crore
๐Ÿ”ด International system uses million and billion
๐Ÿ”ต Estimation simplifies calculations

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TEXTBOOK QUESTIONS

๐ŸŒฟ 1.1 A LAKH VARIETIES!

๐Ÿ”’ โ“ Question 1.
According to the 2011 Census, the population of the town of Chintamani was about 75,000. How much less than one lakh is 75,000?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น One lakh = 1,00,000
๐Ÿ”น Given population = 75,000
๐Ÿ”น Difference = 1,00,000 โˆ’ 75,000
๐Ÿ”ธ = 25,000

โœ”๏ธ Final: 75,000 is 25,000 less than one lakh.

๐Ÿ”’ โ“ Question 2.
The estimated population of Chintamani in the year 2024 is 1,06,000. How much more than one lakh is 1,06,000?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น One lakh = 1,00,000
๐Ÿ”น Estimated population = 1,06,000
๐Ÿ”น Difference = 1,06,000 โˆ’ 1,00,000
๐Ÿ”ธ = 6,000

โœ”๏ธ Final: 1,06,000 is 6,000 more than one lakh.

๐Ÿ”’ โ“ Question 3.
By how much did the population of Chintamani increase from 2011 to 2024?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Population in 2011 = 75,000
๐Ÿ”น Population in 2024 = 1,06,000
๐Ÿ”น Increase = 1,06,000 โˆ’ 75,000
๐Ÿ”ธ = 31,000

โœ”๏ธ Final: The population increased by 31,000 from 2011 to 2024.

๐ŸŒฟ 1.2 LAND OF TENS

๐Ÿ”’ โ“ Figure it Out (a)
For the number 8300, write expressions for at least two different ways to obtain the number through button clicks.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Way 1: (83 ร— 100) = 8300
๐Ÿ”น Way 2: (8 ร— 1000) + (3 ร— 100) = 8300

๐Ÿ”’ โ“ Figure it Out (b)
For the number 40629, write expressions for at least two different ways to obtain the number through button clicks.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Way 1: (40 ร— 1000) + (6 ร— 100) + (2 ร— 10) + (9 ร— 1) = 40629
๐Ÿ”น Way 2: (4 ร— 10000) + (62 ร— 10) + (9 ร— 1) = 40629

๐Ÿ”’ โ“ Figure it Out (c)
For the number 56354, write expressions for at least two different ways to obtain the number through button clicks.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Way 1: (56 ร— 1000) + (3 ร— 100) + (5 ร— 10) + (4 ร— 1) = 56354
๐Ÿ”น Way 2: (5 ร— 10000) + (63 ร— 100) + (5 ร— 10) + (4 ร— 1) = 56354

๐Ÿ”’ โ“ Figure it Out (d)
For the number 66666, write expressions for at least two different ways to obtain the number through button clicks.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Way 1: (6 ร— 10000) + (6 ร— 1000) + (6 ร— 100) + (6 ร— 10) + (6 ร— 1) = 66666
๐Ÿ”น Way 2: (66 ร— 1000) + (6 ร— 100) + (6 ร— 10) + (6 ร— 1) = 66666

๐Ÿ”’ โ“ Figure it Out (e)
For the number 367813, write expressions for at least two different ways to obtain the number through button clicks.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Way 1: (3 ร— 100000) + (6 ร— 10000) + (7 ร— 1000) + (8 ร— 100) + (1 ร— 10) + (3 ร— 1) = 367813
๐Ÿ”น Way 2: (367 ร— 1000) + (8 ร— 100) + (1 ร— 10) + (3 ร— 1) = 367813

๐Ÿ”’ โ“ Question 1.
For the numbers in the previous exercise, find out how to get each number by making the smallest number of button clicks and write the expression.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น 8300
๐Ÿ”ธ (8 ร— 1000) + (3 ร— 100) = 8300

๐Ÿ”น 40629
๐Ÿ”ธ (4 ร— 10000) + (0 ร— 1000) + (6 ร— 100) + (2 ร— 10) + (9 ร— 1) = 40629

๐Ÿ”น 56354
๐Ÿ”ธ (5 ร— 10000) + (6 ร— 1000) + (3 ร— 100) + (5 ร— 10) + (4 ร— 1) = 56354

๐Ÿ”น 66666
๐Ÿ”ธ (6 ร— 10000) + (6 ร— 1000) + (6 ร— 100) + (6 ร— 10) + (6 ร— 1) = 66666

๐Ÿ”น 367813
๐Ÿ”ธ (3 ร— 100000) + (6 ร— 10000) + (7 ร— 1000) + (8 ร— 100) + (1 ร— 10) + (3 ร— 1) = 367813

๐Ÿ”’ โ“ Question 2.
Do you see any connection between each number and the corresponding smallest number of button clicks?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น The smallest number of button clicks is obtained by using the place value of each digit.
๐Ÿ”น Each digit tells how many times a particular place-value button is pressed.
๐Ÿ”น This avoids unnecessary extra button presses and gives the minimum total clicks.

๐Ÿ”’ โ“ Question 3.
If you notice, the expressions for the least button clicks also give the Indian place value notation of the numbers. Think about why this is so.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Indian place value notation breaks a number into digits multiplied by their place values.
๐Ÿ”น Creative Chittiโ€™s buttons exactly match these place values (+1, +10, +100, +1000, โ€ฆ).
๐Ÿ”น Therefore, using the least button clicks naturally follows the Indian place value system.

๐ŸŒฟ 1.3 OF CRORES AND CRORES!

๐Ÿ”’ โ“ Question 1.
Read the following numbers in Indian place value notation and write their number names in both the Indian and American systems.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น (a) 4050678
๐Ÿ”ธ Indian system: Forty lakh fifty thousand six hundred seventy eight
๐Ÿ”ธ American system: Four million fifty thousand six hundred seventy eight

๐Ÿ”น (b) 48121620
๐Ÿ”ธ Indian system: Four crore eighty one lakh twenty one thousand six hundred twenty
๐Ÿ”ธ American system: Forty eight million one hundred twenty one thousand six hundred twenty

๐Ÿ”น (c) 20022002
๐Ÿ”ธ Indian system: Two crore two thousand two
๐Ÿ”ธ American system: Twenty million twenty two thousand two

๐Ÿ”น (d) 246813579
๐Ÿ”ธ Indian system: Twenty four crore sixty eight lakh thirteen thousand five hundred seventy nine
๐Ÿ”ธ American system: Two hundred forty six million eight hundred thirteen thousand five hundred seventy nine

๐Ÿ”น (e) 345000543
๐Ÿ”ธ Indian system: Thirty four crore fifty lakh five hundred forty three
๐Ÿ”ธ American system: Three hundred forty five million five hundred forty three

๐Ÿ”น (f) 1020304050
๐Ÿ”ธ Indian system: One hundred two crore three lakh four thousand fifty
๐Ÿ”ธ American system: One billion twenty million three hundred four thousand fifty

๐Ÿ”’ โ“ Question 2.
Write the following numbers in Indian place value notation.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น (a) One crore one lakh one thousand ten
๐Ÿ”ธ 1,01,01,010

๐Ÿ”น (b) One billion one million one thousand one
๐Ÿ”ธ 1,00,10,01,001

๐Ÿ”น (c) Ten crore twenty lakh thirty thousand forty
๐Ÿ”ธ 10,20,30,040

๐Ÿ”น (d) Nine billion eighty million seven hundred thousand six hundred
๐Ÿ”ธ 90,80,07,00,600

๐Ÿ”’ โ“ Question 3.
Compare and write โ€˜<โ€™, โ€˜>โ€™ or โ€˜=โ€™.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น (a) 30 thousand < 3 lakhs
๐Ÿ”น (b) 500 lakhs = 5 million
๐Ÿ”น (c) 800 thousand < 8 million
๐Ÿ”น (d) 640 crore > 60 billion

๐ŸŒฟ 1.5 PATTERNS IN PRODUCTS

๐Ÿ”’ โ“ Figure it Out โ€” Question 1
Find quick ways to calculate these products.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น (a) 2 ร— 1768 ร— 50
๐Ÿ”ธ (2 ร— 50) ร— 1768 = 100 ร— 1768 = 176800

๐Ÿ”น (b) 72 ร— 125
๐Ÿ”ธ 125 = 1000 / 8
๐Ÿ”ธ 72 ร— (1000 / 8) = 9 ร— 1000 = 9000

๐Ÿ”น (c) 125 ร— 40 ร— 8 ร— 25
๐Ÿ”ธ (125 ร— 8) ร— (40 ร— 25)
๐Ÿ”ธ 1000 ร— 1000 = 1000000

๐Ÿ”’ โ“ Figure it Out โ€” Question 2
Calculate these products quickly.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น (a) 25 ร— 12
๐Ÿ”ธ (100 / 4) ร— 12 = 300
โœ”๏ธ Final: 300

๐Ÿ”น (b) 25 ร— 240
๐Ÿ”ธ (100 / 4) ร— 240 = 6000
โœ”๏ธ Final: 6000

๐Ÿ”น (c) 250 ร— 120
๐Ÿ”ธ (1000 / 4) ร— 120 = 30000
โœ”๏ธ Final: 30000

๐Ÿ”น (d) 2500 ร— 12
๐Ÿ”ธ (10000 / 4) ร— 12 = 30000
โœ”๏ธ Final: 30000

๐Ÿ”น (e) _____ ร— _____ = 12000000
๐Ÿ”ธ 12000 ร— 1000 = 12000000

๐ŸŒฟ 1.6 DID YOU EVER WONDER…?

๐Ÿ”’ โ“ Question 1
Using all digits from 0โ€“9 exactly once (the first digit cannot be 0) to create a 10-digit number, write theโ€”
(a) Largest multiple of 5
(b) Smallest even number

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น (a) Largest multiple of 5
๐Ÿ”ธ A multiple of 5 must end in 0 or 5.
๐Ÿ”ธ To make the number largest, place the largest digits in the highest places.
๐Ÿ”ธ Ending with 0 gives a larger number than ending with 5.
๐Ÿ”ธ Arrange remaining digits from 9 to 1 in descending order.

โœ”๏ธ Final: 9876543210

๐Ÿ”น (b) Smallest even number
Smallest even number

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น The number must use digits 0โ€“9 exactly once, and the first digit cannot be 0.
๐Ÿ”น To make it smallest, keep the smallest digits as early as possible: start with 1, then 0, then 2, 3, 4, 5, 6, 7.
๐Ÿ”น The last digit must be even, so place 8 at the end and keep 9 just before it.

๐Ÿ“Œ โœ… Final: 1023456798

๐Ÿ”’ โ“ Question 2
The number 10,30,285 in words is Ten lakhs thirty thousand two hundred eighty five, which has 43 letters. Give a 7-digit number name which has the maximum number of letters.

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น Comparing long 7-digit number names shows that the word โ€œseventyโ€ (7 letters) repeated many times gives more letters than โ€œninetyโ€ (6 letters).
๐Ÿ”น The number 7,777,777 uses seventy and seven repeatedly along with lakh, thousand, and hundred, making its name very long.

๐Ÿ”น In words (Indian system):
Seventy seven lakh seventy seven thousand seven hundred seventy seven

๐Ÿ“Œ โœ… Final: 7,777,777

๐Ÿ”’ โ“ Question 3
Write a 9-digit number where exchanging any two digits results in a bigger number. How many such numbers exist?

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น For the number to increase after any exchange, the original number must be:
๐Ÿ”ธ Arranged in strictly increasing order from left to right.

๐Ÿ”น Smallest digits on the left, largest on the right.

๐Ÿ”น Example:
๐Ÿ”ธ 123456789

๐Ÿ”น Any swap will move a larger digit to a higher place value, making the number larger.

๐Ÿ”น Count of such numbers:
๐Ÿ”ธ Only one such arrangement is possible using digits 1โ€“9 once.

โœ”๏ธ Final:
๐Ÿ”น Number: 123456789
๐Ÿ”น Total such numbers: 1

๐Ÿ”’ โ“ Question 4
Strike out 10 digits from the number 12345123451234512345 so that the remaining number is as large as possible.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น We must delete 10 digits and keep 10 digits in the same order (a subsequence).
๐Ÿ”น To maximize the remaining 10-digit number, keep the earliest possible high digits (5s), while still leaving enough digits to complete 10 places.
๐Ÿ”น The largest possible remaining 10-digit number is obtained by keeping digits that form:

๐Ÿ“Œ โœ… Final: 5534512345

๐Ÿ”’ โ“ Question 5
The words โ€˜zeroโ€™ and โ€˜oneโ€™ share letters โ€˜eโ€™ and โ€˜oโ€™. The words โ€˜oneโ€™ and โ€˜twoโ€™ share a letter โ€˜oโ€™, and the words โ€˜twoโ€™ and โ€˜threeโ€™ also share a letter โ€˜tโ€™. How far do you have to count to find two consecutive numbers which do not share an English letter in common?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Checking consecutive number-names in standard English spelling shows that every consecutive pair shares at least one common letter.
๐Ÿ”น This overlap continues because the same letters keep recurring in number words across ones, tens, hundreds, thousands, etc.

โœ”๏ธ Final: You cannot find such a pair of consecutive numbers (so there is no finite counting point where this happens).

๐Ÿ”’ โ“ Question 6
Suppose you write down all the numbers 1, 2, 3, 4, …, 9, 10, 11, …
The tenth digit you write is โ€˜1โ€™ and the eleventh digit is โ€˜0โ€™, as part of the number 10.

(a) What would the 1000th digit be? At which number would it occur?
(b) What number would contain the millionth digit?
(c) When would you have written the digit โ€˜5โ€™ for the 5000th time?

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น (a) 1000th digit
๐Ÿ”ธ Digits from 1 to 9 = 9
๐Ÿ”ธ Digits from 10 to 99 = 90 ร— 2 = 180
๐Ÿ”ธ Total digits up to 99 = 9 + 180 = 189
๐Ÿ”ธ Position inside 3-digit numbers = 1000 โˆ’ 189 = 811
๐Ÿ”ธ Each 3-digit number gives 3 digits
๐Ÿ”ธ Number offset = (811 โˆ’ 1) รท 3 = 270
๐Ÿ”ธ Digit position inside the number = (811 โˆ’ 1) mod 3 = 0 (first digit)
๐Ÿ”ธ Number = 100 + 270 = 370
๐Ÿ”ธ First digit of 370 = 3

โœ”๏ธ Final: 1000th digit is 3, and it occurs in the number 370

๐Ÿ”น (b) millionth digit
๐Ÿ”ธ Digits up to 9 = 9
๐Ÿ”ธ Digits from 10 to 99 = 180
๐Ÿ”ธ Digits from 100 to 999 = 900 ร— 3 = 2700
๐Ÿ”ธ Total up to 999 = 9 + 180 + 2700 = 2889
๐Ÿ”ธ Digits from 1000 to 9999 = 9000 ร— 4 = 36000
๐Ÿ”ธ Total up to 9999 = 2889 + 36000 = 38889
๐Ÿ”ธ Digits from 10000 to 99999 = 90000 ร— 5 = 450000
๐Ÿ”ธ Total up to 99999 = 38889 + 450000 = 488889
๐Ÿ”ธ Millionth position inside 6-digit numbers = 1000000 โˆ’ 488889 = 511111
๐Ÿ”ธ Each 6-digit number gives 6 digits
๐Ÿ”ธ Number offset = (511111 โˆ’ 1) รท 6 = 85185
๐Ÿ”ธ Number = 100000 + 85185 = 185185

โœ”๏ธ Final: The millionth digit is contained in the number 185185

๐Ÿ”น (c) digit โ€˜5โ€™ for the 5000th time

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Count of digit โ€˜5โ€™ written from 1 up to 13494 is 4999.
๐Ÿ”น The next number 13495 adds one more โ€˜5โ€™, making the total 5000.

โœ”๏ธ Final: The digit โ€˜5โ€™ is written for the 5000th time while writing the number 13495.

๐Ÿ”’ โ“ Question 7
A calculator has only โ€˜+10,000โ€™ and โ€˜+100โ€™ buttons. Write an expression describing the number of button clicks to be made for the following numbers:

(a) 20,800
(b) 92,100
(c) 1,20,500
(d) 65,30,000
(e) 70,25,700

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น (a) 20,800
๐Ÿ”ธ 2 ร— 10,000 = 20,000
๐Ÿ”ธ 8 ร— 100 = 800
๐Ÿ”ธ 20,000 + 800 = 20,800
๐Ÿ“Œ โœ… Final: 2 clicks of +10,000 and 8 clicks of +100

๐Ÿ”น (b) 92,100
๐Ÿ”ธ 9 ร— 10,000 = 90,000
๐Ÿ”ธ 21 ร— 100 = 2,100
๐Ÿ”ธ 90,000 + 2,100 = 92,100
๐Ÿ“Œ โœ… Final: 9 clicks of +10,000 and 21 clicks of +100

๐Ÿ”น (c) 1,20,500
๐Ÿ”ธ 12 ร— 10,000 = 1,20,000
๐Ÿ”ธ 5 ร— 100 = 500
๐Ÿ”ธ 1,20,000 + 500 = 1,20,500
๐Ÿ“Œ โœ… Final: 12 clicks of +10,000 and 5 clicks of +100

๐Ÿ”น (d) 65,30,000
๐Ÿ”ธ 653 ร— 10,000 = 65,30,000
๐Ÿ“Œ โœ… Final: 653 clicks of +10,000 and 0 clicks of +100

๐Ÿ”น (e) 70,25,700
๐Ÿ”ธ 702 ร— 10,000 = 70,20,000
๐Ÿ”ธ 57 ร— 100 = 5,700
๐Ÿ”ธ 70,20,000 + 5,700 = 70,25,700
๐Ÿ“Œ โœ… Final: 702 clicks of +10,000 and 57 clicks of +100

๐Ÿ”’ โ“ Question 8
How many lakhs make a billion?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น 1 lakh = 100,000
๐Ÿ”น 1 billion = 1,000,000,000
๐Ÿ”น Number of lakhs in a billion = 1,000,000,000 รท 100,000 = 10,000

โœ”๏ธ Final: 10,000 lakhs

๐Ÿ”’ โ“ Question 9
You are given two sets of number cards numbered from 1โ€“9. Place a number card in each box below to get the (a) largest possible sum
(b) smallest possible difference of the two resulting numbers.

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น (a) Largest possible sum
๐Ÿ”ธ Make both numbers as large as possible by placing the largest digits in the highest places (each set used separately).
โœ”๏ธ Final: 7-digit number = 9876543, 5-digit number = 98765

๐Ÿ”น (b) Smallest possible difference
๐Ÿ”ธ To minimize the difference, make the 7-digit number as small as possible and the 5-digit number as large as possible (each from its own set).
โœ”๏ธ Final: 7-digit number = 1234567, 5-digit number = 98765

๐Ÿ”’ โ“ Question 10
You are given some number cards; 4000, 13000, 300, 70000, 150000, 20, 5. Using the cards get as close as you can to the numbers below using any operation you want. Each card can be used only once for making a particular number.
(a) 1,10,000: Closest I could make is 4000 ร— (20 + 5) + 13000
= 1,13,000
(b) 2,00,000:
(c) 5,80,000:
(d) 12,45,000:
(e) 20,90,800:

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น (b) 2,00,000
๐Ÿ”ธ 150000 + 70000 = 220000
๐Ÿ”ธ 4000 ร— 5 = 20000
๐Ÿ”ธ 220000 โˆ’ 20000 = 200000
๐Ÿ“Œ โœ… Final: 150000 + 70000 โˆ’ (4000 ร— 5) = 2,00,000

๐Ÿ”น (c) 5,80,000
๐Ÿ”ธ 70000 ร— 5 = 350000
๐Ÿ”ธ 4000 ร— 20 = 80000
๐Ÿ”ธ 150000 + 350000 = 500000
๐Ÿ”ธ 500000 + 80000 = 580000
๐Ÿ“Œ โœ… Final: 150000 + (70000 ร— 5) + (4000 ร— 20) = 5,80,000

๐Ÿ”น (d) 12,45,000 (closest)
๐Ÿ”ธ 70000 + 150000 = 220000
๐Ÿ”ธ 220000 + 13000 = 233000
๐Ÿ”ธ 233000 ร— 5 = 1165000
๐Ÿ”ธ 4000 ร— 20 = 80000
๐Ÿ”ธ 1165000 + 80000 = 1245000
๐Ÿ”ธ 1245000 + 300 = 1245300
๐Ÿ”ธ Difference from 12,45,000 = 1245300 โˆ’ 1245000 = 300
๐Ÿ“Œ โœ… Final: 5 ร— (150000 + 70000 + 13000) + (4000 ร— 20) + 300 = 12,45,300 (300 more)

๐Ÿ”น (e) 20,90,800 (closest)
๐Ÿ”ธ 13000 + 150000 = 163000
๐Ÿ”ธ 163000 ร— 5 = 815000
๐Ÿ”ธ 20 + 4000 = 4020
๐Ÿ”ธ 4020 ร— 300 = 1206000
๐Ÿ”ธ 1206000 + 70000 = 1276000
๐Ÿ”ธ 815000 + 1276000 = 2091000
๐Ÿ”ธ Difference from 20,90,800 = 2091000 โˆ’ 2090800 = 200
๐Ÿ“Œ โœ… Final: 5 ร— (150000 + 13000) + (300 ร— (4000 + 20)) + 70000 = 20,91,000 (200 more)

๐Ÿ”’ โ“ Question 11
Find out how many coins should be stacked to match the height of the Statue of Unity. Assume each coin is 1 mm thick.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Height of Statue of Unity = 182 m
๐Ÿ”น 1 mm = 0.001 m
๐Ÿ”ธ Number of coins = 182 รท 0.001
๐Ÿ”ธ Number of coins = 182000
๐Ÿ“Œ โœ… Final: 1,82,000 coins

๐Ÿ”’ โ“ Question 12
Grey-headed albatrosses have a roughly 7-feet wide wingspan. They are known to migrate across several oceans. Albatrosses can cover about 900โ€“1000 km in a day. One of the longest single trips recorded is about 12,000 km. How many days would such a trip take to cross the Pacific Ocean approximately?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Fast estimate (1000 km/day):
๐Ÿ”ธ Days = 12000 รท 1000
๐Ÿ”ธ Days = 12

๐Ÿ”น Slow estimate (900 km/day):
๐Ÿ”ธ Days = 12000 รท 900
๐Ÿ”ธ Days = 13.33 (approx)

๐Ÿ“Œ โœ… Final: Approximately 12 to 14 days

๐Ÿ”’ โ“ Question 13
A bar-tailed godwit holds the record for the longest recorded non-stop flight. It travelled 13,560 km from Alaska to Australia without stopping. Its journey started on 13 October 2022 and continued for about 11 days. Find out the approximate distance it covered every day. Find out the approximate distance it covered every hour.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Approximate distance per day
๐Ÿ”ธ Total distance = 13560 km
๐Ÿ”ธ Total time = 11 days
๐Ÿ”ธ Distance per day = 13560/11 km
๐Ÿ”ธ Distance per day = 1232.727… km
๐Ÿ“Œ โœ… Final: Approximately 1233 km per day

๐Ÿ”น Approximate distance per hour
๐Ÿ”ธ Total hours in 11 days = 11 ร— 24
๐Ÿ”ธ Total hours = 264
๐Ÿ”ธ Distance per hour = 13560/264 km
๐Ÿ”ธ Distance per hour = 51.3636… km
๐Ÿ“Œ โœ… Final: Approximately 51 km per hour

๐Ÿ”’ โ“ Question 14
Bald eagles are known to fly as high as 4500โ€“6000 m above the ground level. Mount Everest is about 8850 m high. Aeroplanes can fly as high as 10,000โ€“12,800 m. How many times bigger are these heights compared to Somuโ€™s building?

๐Ÿ“Œ โœ… Answer:

๐Ÿ”น From the lesson context, Somuโ€™s building height = 10 m.

๐Ÿ”น Bald eagles
๐Ÿ”ธ 4500 รท 10 = 450
๐Ÿ”ธ 6000 รท 10 = 600
๐Ÿ“Œ โœ… Final: Bald eagles fly about 450โ€“600 times higher than Somuโ€™s building.

๐Ÿ”น Mount Everest
๐Ÿ”ธ 8850 รท 10 = 885
๐Ÿ“Œ โœ… Final: Mount Everest is about 885 times higher than Somuโ€™s building.

๐Ÿ”น Aeroplanes
๐Ÿ”ธ 10000 รท 10 = 1000
๐Ÿ”ธ 12800 รท 10 = 1280
๐Ÿ“Œ โœ… Final: Aeroplanes fly about 1000โ€“1280 times higher than Somuโ€™s building.

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OTHER IMPORTANT QUESTIONS

( MODEL QUESTION PAPER )

ESPECIALLY MADE FROM THIS CHAPTER ONLY

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

๐Ÿ”’ โ“ Question 1
What is the place value of 7 in the number 7,53,214?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น The digit 7 is in the lakh place
๐Ÿ”น Place value of 7 = 7 ร— 1,00,000
๐Ÿ”น Place value = 7,00,000

๐Ÿ”’ โ“ Question 2
Write the smallest 6-digit number.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น The smallest 6-digit number is 1,00,000

๐Ÿ”’ โ“ Question 3
How many zeros are there in one crore?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น One crore has 7 zeros

๐Ÿ”’ โ“ Question 4
Write 3,45,00,000 in words (Indian system).

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Three crore forty-five lakh

๐Ÿ”’ โ“ Question 5
Which number is greater: 9,87,654 or 9,78,456?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Both numbers have 6 digits
๐Ÿ”น At the ten-thousands place, 8 > 7
๐Ÿ”น 9,87,654 is greater

๐Ÿ”’ โ“ Question 6
Round 6,48,372 to the nearest thousand.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Hundreds digit is 3
๐Ÿ”น Rounded value = 6,48,000


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

๐Ÿ”’ โ“ Question 7
Write the place value of each digit in 4,62,815.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น 4 = 4,00,000
๐Ÿ”น 6 = 60,000
๐Ÿ”น 2 = 2,000
๐Ÿ”น 8 = 800
๐Ÿ”น 1 = 10
๐Ÿ”น 5 = 5

๐Ÿ”’ โ“ Question 8
Write in numerals: Seven crore eight lakh six thousand forty-two.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Seven crore = 7,00,00,000
๐Ÿ”น Eight lakh = 8,00,000
๐Ÿ”น Six thousand = 6,000
๐Ÿ”น Forty-two = 42
๐Ÿ”น Number = 7,08,06,042

๐Ÿ”’ โ“ Question 9
Arrange in ascending order: 3,45,678; 3,54,768; 3,47,568.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Compare digit by digit from left
๐Ÿ”น Ascending order
๐Ÿ”น 3,45,678 < 3,47,568 < 3,54,768

๐Ÿ”’ โ“ Question 10
Write 5,03,08,019 in words.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Five crore three lakh eight thousand nineteen

๐Ÿ”’ โ“ Question 11
Find the difference between the Indian and International place value systems.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Indian system uses lakh and crore
๐Ÿ”น International system uses million and billion

๐Ÿ”’ โ“ Question 12
Round 9,84,216 to the nearest ten thousand.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Thousands digit is 4
๐Ÿ”น Rounded value = 9,80,000


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

๐Ÿ”’ โ“ Question 13
Write the number name of 6,08,45,219.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Six crore eight lakh forty-five thousand two hundred nineteen

๐Ÿ”’ โ“ Question 14
Compare 8,25,416 and 8,52,164 using place value.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Both numbers have 6 digits
๐Ÿ”น At the ten-thousands place, 2 < 5
๐Ÿ”น 8,52,164 is greater

๐Ÿ”’ โ“ Question 15
Write in numerals: Ninety-two million four hundred six thousand eight.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Ninety-two million = 92,000,000
๐Ÿ”น Four hundred six thousand = 406,000
๐Ÿ”น Eight = 8
๐Ÿ”น Number = 92,406,008

๐Ÿ”’ โ“ Question 16
Round 7,48,962 to the nearest lakh.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Ten-thousands digit is 4
๐Ÿ”น Rounded value = 7,00,000

๐Ÿ”’ โ“ Question 17
Write any three uses of large numbers in daily life.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Population counting
๐Ÿ”น Government budgeting
๐Ÿ”น Distance measurement in space

๐Ÿ”’ โ“ Question 18
Write the expanded form of 5,03,207.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น 5,00,000 + 3,000 + 200 + 7

๐Ÿ”’ โ“ Question 19
Write the successor of 9,99,999.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Successor = 10,00,000

๐Ÿ”’ โ“ Question 20
Explain why estimation is useful.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น It makes calculations easier
๐Ÿ”น It saves time
๐Ÿ”น It gives a close approximate value

๐Ÿ”’ โ“ Question 21
Write the number with 6 in lakh place and 4 in hundred place.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น One such number is 6,00,400

๐Ÿ”’ โ“ Question 22
What is the face value of 8 in 8,73,945?

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Face value of 8 is 8


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

๐Ÿ”’ โ“ Question 23
Write the number 7,84,26,513 in expanded form and words.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Expanded form
๐Ÿ”ธ 7,00,00,000 + 80,00,000 + 4,00,000 + 20,000 + 6,000 + 500 + 10 + 3
๐Ÿ”น In words
๐Ÿ”ธ Seven crore eighty-four lakh twenty-six thousand five hundred thirteen

๐Ÿ”’ โ“ Question 24
Arrange 6,48,921; 6,84,219; 6,49,218 in descending order.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Compare from leftmost digit
๐Ÿ”น Descending order
๐Ÿ”ธ 6,84,219 > 6,49,218 > 6,48,921

๐Ÿ”’ โ“ Question 25
Explain the Indian place value system with an example.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Indian system uses ones, tens, hundreds, thousands, lakhs, crores
๐Ÿ”น Example: 3,45,67,218
๐Ÿ”ธ Three crore forty-five lakh sixty-seven thousand two hundred eighteen

๐Ÿ”’ โ“ Question 26
Round 9,63,417 to the nearest ten thousand and explain the steps.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Ten-thousands digit is 6
๐Ÿ”น Thousands digit is 3
๐Ÿ”น Rounded value = 9,60,000

๐Ÿ”’ โ“ Question 27
Write five mistakes students should avoid while dealing with large numbers.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Wrong comma placement
๐Ÿ”น Mixing number systems
๐Ÿ”น Missing zeros
๐Ÿ”น Wrong rounding
๐Ÿ”น Incorrect reading

๐Ÿ”’ โ“ Question 28
Write the predecessor and successor of 10,00,000.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Predecessor = 9,99,999
๐Ÿ”น Successor = 10,00,001

๐Ÿ”’ โ“ Question 29
Explain how large numbers help us understand real-world data.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Used in population data
๐Ÿ”น Used in science and space
๐Ÿ”น Used in economics and planning

๐Ÿ”’ โ“ Question 30
Write 8,03,47,615 in words and international system.

๐Ÿ“Œ โœ… Answer:
๐Ÿ”น Indian system
๐Ÿ”ธ Eight crore three lakh forty-seven thousand six hundred fifteen
๐Ÿ”น International system
๐Ÿ”ธ Eighty million three hundred forty-seven thousand six hundred fifteen

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