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Chapter 1

Number System — Exercise 1(A)

Class - 6 RS Aggarwal Mathematics Solutions



Exercise 1(A)

Question 1

Write the numeral for each of the following :

(i) Eight lakh five thousand twelve.

(ii) Thirteen lakh three thousand eight.

(iii) Three crore three lakh three thousand three.

(iv) Five crore twelve lakh eighteen.

(v) Nine crore nineteen lakh five thousand eight.

(vi) Six crore thirty five lakh nineteen thousand sixteen.

(vii) Eleven crore twenty two lakh thirty three thousand four hundred fifty.

Answer

(i) Eight lakh five thousand twelve: 8,05,012

(ii) Thirteen lakh three thousand eight: 13,03,008

(iii) Three crore three lakh three thousand three: 3,03,03,003

(iv) Five crore twelve lakh eighteen: 5,12,00,018

(v) Nine crore nineteen lakh five thousand eight: 9,19,05,008

(vi) Six crore thirty five lakh nineteen thousand sixteen: 6,35,19,016

(vii) Eleven crore twenty two lakh thirty three thousand four hundred fifty: 11,22,33,450

Question 2

Write each of the following in words :

(i) 8,08,080

(ii) 15,07,063

(iii) 87,08,109

(iv) 2,14,05,063

(v) 3,03,03,103

(vi) 10,06,05,368

Answer

(i) 8,08,080: Eight lakh eight thousand eighty.

(ii) 15,07,063: Fifteen lakh seven thousand sixty-three.

(iii) 87,08,109: Eighty-seven lakh eight thousand one hundred nine.

(iv) 2,14,05,063: Two crore fourteen lakh five thousand sixty-three.

(v) 3,03,03,103: Three crore three lakh three thousand one hundred three.

(vi) 10,06,05,368: Ten crore six lakh five thousand three hundred sixty-eight.

Question 3(i)

Write the place value of 4 in 8,46,572.

Answer

Counting from the right in 8,46,572 :

2 is in the ones place.

7 is in the tens place.

5 is in the hundreds place.

6 is in the thousands place.

4 is in the ten thousands place.

Hence, the place value of 4 in 8,46,572 is 40,000.

Question 3(ii)

Write the place value of 7 in 7,30,493.

Answer

Counting from the right in 7,30,493 :

3 is in the ones place.

9 is in the tens place.

4 is in the hundreds place.

0 is in the thousands place.

3 is in the ten thousands place.

7 is in the lakhs place.

Hence, the place value of 7 in 7,30,493 is 7,00,000.

Question 3(iii)

Write the place value of 6 in 23,76,400.

Answer

Counting from the right in 23,76,400 :

0 is in the ones place.

0 is in the tens place.

4 is in the hundreds place.

6 is in the thousands place.

7 is in the ten thousands place.

3 is in the lakhs place.

2 is in the ten lakhs place.

Hence, the place value of 6 in 23,76,400 is 6,000.

Question 3(iv)

Write the place value of 9 in 19,63,605.

Answer

Counting from the right in 19,63,605 :

5 is in the ones place.

0 is in the tens place.

6 is in the hundreds place.

3 is in the thousands place.

6 is in the ten thousands place.

9 is in the lakhs place.

1 is in the ten lakhs place.

Hence, the place value of 9 in 19,63,605 is 9,00,000.

Question 3(v)

Write the place value of 8 in 20,07,189.

Answer

Counting from the right in 20,07,189 :

9 is in the ones place.

8 is in the tens place.

1 is in the hundreds place.

7 is in the thousands place.

0 is in the ten thousands place.

0 is in the lakhs place.

2 is in the ten lakhs place.

Hence, the place value of 8 in 20,07,189 is 80.

Question 3(vi)

Write the place value of 3 in 23,608.

Answer

Counting from the right in 23,608 :

8 is in the ones place.

0 is in the tens place.

6 is in the hundreds place.

3 is in the thousands place.

2 is in the ten thousands place.

Hence, the place value of 3 in 23,608 is 3,000.

Question 4

Find the difference between the place-values of two sixes in 6,56,348.

Answer

In 6,56,348, counting from the right:

8 is in the ones place.

4 is in the tens place.

3 is in the hundreds place.

6 is in the thousands place.

So, its place value is 6 × 1,000 = 6,000.

5 is in the ten thousands place.

6 is in the lakhs place.

So, its place value is 6 × 1,00,000 = 6,00,000.

Difference between the place-values of two sixes in 6,56,348 = 6,00,000 - 6,000 = 5,94,000

Hence, the difference between the place-values of two sixes in 6,56,348 is 5,94,000.

Question 5

Find the difference between the place-value and the face-value of 8 in the numeral 5,86,273.

Answer

In the numeral 5,86,273, the digit '8' is in the ten thousands place.

So, its place value is 8 × 10,000 = 80,000.

The face value of a digit is the digit itself.

So, the face value of '8' is 8.

Difference = Place-value - Face-value

Difference = 80,000 − 8

Difference = 79,992

Hence, the difference between the place-value and the face-value of 8 in the numeral 5,86,273 = 79,992.

Question 6

Write each of the following in expanded form :

(i) 5,16,287

(ii) 13,25,694

(iii) 8,08,808

(iv) 64,72,319

(v) 1,36,04,107

(vi) 9,36,50,519

Answer

(i) Expanding,

5,16,287 = 5 × 1,00,000 + 1 × 10,000 + 6 × 1,000 + 2 × 100 + 8 × 10+ 7 × 1

= 5,00,000 + 10,000 + 6,000 + 200 + 80 + 7.

(ii) Expanding,

13,25,694 = 1 × 10,00,000 + 3 × 1,00,000 + 2 × 10,000 + 5 × 1,000 + 6 × 100 + 9 × 10 + 4 × 1

= 10,00,000 + 3,00,000 + 20,000 + 5,000 + 600 + 90 + 4.

(iii) Expanding,

8,08,808 = 8 × 1,00,000 + 0 × 10,000 + 8 × 1,000 + 8 × 100 + 0 × 10 + 8 × 1

= 8,00,000 + 8,000 + 800 + 8.

(iv) Expanding,

64,72,319 = 6 × 10,00,000 + 4 × 1,00,000 + 7 × 10,000 + 2 × 1,000 + 3 × 100 + 1 × 10 + 9 × 1

= 60,00,000 + 4,00,000 + 70,000 + 2,000 + 300 + 10 + 9.

(v) Expanding,

1,36,04,107 = 1 × 1,00,00,000 + 3 × 10,00,000 + 6 × 1,00,000 + 0 × 10,000 + 4 × 1,000 + 1 × 100 + 0 × 10 + 7 × 1

= 1,00,00,000 + 30,00,000 + 6,00,000 + 4,000 + 100 + 7.

(vi) Expanding,

9,36,50,519 = 9 × 1,00,00,000 + 3 × 10,00,000 + 6 × 1,00,000 + 5 × 10,000 + 0 × 1,000 + 5 × 100 + 1 × 10 + 9 × 1

= 9,00,00,000 + 30,00,000 + 6,00,000 + 50,000 + 500 + 10 + 9.

Question 7(i)

Write the number corresponding to :

(5 × 1,00,000) + (1 × 10,000) + (4 × 1,000) + (7 × 100) + (3 × 10) + (8 × 1).

Answer

To find the number corresponding to the expanded form, we will calculate each term and then sum them up:

5 × 1,00,000 = 5,00,000

1 × 10,000 = 10,000

4 × 1,000 = 4,000

7 × 100 = 700

3 × 10 = 30

8 × 1 = 8

Now, add these values together:

5,00,000 + 10,000 + 4,000 + 700 + 30 + 8 = 5,14,738

Hence, the number corresponding to the given expanded form is 5,14,738.

Question 7(ii)

Write the number corresponding to :

(6 × 1,00,000) + (6 × 1,000) + (3 × 10) + (6 × 1).

Answer

To find the number corresponding to the expanded form, we will calculate each term and then sum them up:

6 × 1,00,000 = 6,00,000

6 × 1,000 = 6,000

3 × 10 = 30

6 × 1 = 6

Now, add these values together:

6,00,000 + 6,000 + 30 + 6 = 6,06,036

Hence, the number corresponding to the given expanded form is 6,06,036.

Question 7(iii)

Write the number corresponding to :

(1 × 10,00,000) + (2 × 1,00,000) + (3 × 10,000) + (4 × 100) + (6 × 10) + (9 × 1).

Answer

To find the number corresponding to the expanded form, we will calculate each term and then sum them up:

1 × 10,00,000 = 10,00,000

2 × 1,00,000 = 2,00,000

3 × 10,000 = 30,000

4 × 100 = 400

6 × 10 = 60

9 × 1 = 9

Now, add these values together:

10,00,000 + 2,00,000 + 30,000 + 400 + 60 + 9 = 12,30,469

Hence, the number corresponding to the given expanded form is 12,30,469.

Question 7(iv)

Write the number corresponding to :

(2 × 10,00,000) + (3 × 1,00,000) + (7 × 1,000) + (9 × 100) + (4 × 10) + (5 × 1).

Answer

To find the number corresponding to the expanded form, we will calculate each term and then sum them up:

2 × 10,00,000 = 20,00,000

3 × 1,00,000 = 3,00,000

7 × 1,000 = 7,000

9 × 100 = 900

4 × 10 = 40

5 × 1 = 5

Now, add these values together:

20,00,000 + 3,00,000 + 7,000 + 900 + 40 + 5 = 23,07,945.

Hence, the number corresponding to the given expanded form is 23,07,945.

Question 7(v)

Write the number corresponding to :

(9 × 10,00,000) + (8 × 1,000) + (8 × 100) + (8 × 1).

Answer

To find the number corresponding to the expanded form, we will calculate each term and then sum them up:

9 × 10,00,000 = 90,00,000

8 × 1,000 = 8,000

8 × 100 = 800

8 × 1 = 8

Now, add these values together:

90,00,000 + 8,000 + 800 + 8 = 90,08,808.

Hence, the number corresponding to the given expanded form is 90,08,808.

Question 8

Write the successor of each of the following :

(i) 6,001

(ii) 1,099

(iii) 12,749

(iv) 2,19,708

(v) 62,399

Answer

(i) The successor of 6,001 is 6,001 + 1 = 6,002.

(ii) The successor of 1,099 is 1,099 + 1 = 1,100.

(iii) The successor of 12,749 is 12,749 + 1 = 12,750.

(iv) The successor of 2,19,708 is 2,19,708 + 1 = 2,19,709.

(v) The successor of 62,399 is 62,399 + 1 = 62,400.

Question 9

Write the predecessor of each of the following numbers :

(i) 99

(ii) 1,305

(iii) 32,000

(iv) 1,65,000

Answer

(i) The predecessor of 99 is 99 - 1 = 98.

(ii) The predecessor of 1,305 is 1,305 - 1 = 1,304.

(iii) The predecessor of 32,000 is 32,000 - 1 = 31,999.

(iv) The predecessor of 1,65,000 is 1,65,000 - 1 = 1,64,999.

Question 10

Write the whole number whose successor is :

(i) 100

(ii) 6,299

(iii) 71,650

(iv) 42,000

Answer

(i) The whole number whose successor is 100 is 100 − 1 = 99.

(ii) The whole number whose successor is 6,299 is 6,299 − 1 = 6,298.

(iii) The whole number whose successor is 71,650 is 71,650 − 1 = 71,649.

(iv) The whole number whose successor is 42,000 is 42,000 − 1 = 41,999.

Question 11

Write the whole number whose predecessor is :

(i) 1,000

(ii) 3,189

(iii) 3,001

(iv) 8,000

(v) 9,999

Answer

(i) The whole number whose predecessor is 1,000 is 1,000 + 1 = 1,001.

(ii) The whole number whose predecessor is 3,189 is 3,189 + 1 = 3,190.

(iii) The whole number whose predecessor is 3,001 is 3,001 + 1 = 3,002.

(iv) The whole number whose predecessor is 8,000 is 8,000 + 1 = 8,001.

(v) The whole number whose predecessor is 9,999 is 9,999 + 1 = 10,000.

Question 12

Write down three consecutive whole numbers succeeding 72,597.

Answer

The three consecutive whole numbers succeeding 72,597 are:

  1. 72,597 + 1 = 72,598

  2. 72,598 + 1 = 72,599

  3. 72,599 + 1 = 72,600

Hence, three consecutive whole numbers succeeding 72,597 are 72,598, 72,599 and 72,600.

Question 13

Write down three consecutive whole numbers just preceding 5,10,001.

Answer

To find the three consecutive whole numbers just preceding 5,10,001, we subtract 1 repeatedly:

  1. 5,10,001 - 1 = 5,10,000

  2. 5,10,000 - 1 = 5,09,999

  3. 5,09,999 - 1 = 5,09,998

Hence, the three consecutive whole numbers just preceding 5,10,001 are 5,10,000, 5,09,999, and 5,09,998.

Question 14

How many 6-digit numbers are there in all?

Answer

There are 6-digit numbers from 1,00,000 to 9,99,999, inclusive.

To find the total count, you can use the formula:

Total numbers = (Largest number) - (Smallest number) + 1

Largest 6-digit number = 9,99,999

Smallest 6-digit number = 1,00,000

Total 6-digit numbers = 9,99,999 − 1,00,000 + 1

Total 6-digit numbers = 8,99,999 + 1

Total 6-digit numbers = 9,00,000

Hence, there are 9,00,000 six-digit numbers in all.

Question 15(i)

Write the largest 8-digit number.

Answer

The largest 8-digit number is formed by placing the largest digit (9) in all eight positions.

Hence, the largest 8-digit number is 9,99,99,999.

Question 15(ii)

Write the smallest 8-digit number.

Answer

The smallest 8-digit number is formed by placing the second smallest digit (1) in first position and smallest digit (0) in all remaining positions.

Hence, the smallest 8-digit number is 1,00,00,000.

Question 16

Write all possible 2-digit numbers formed by the digits 3, 7 and 9, when repetition of digits is not allowed.

Answer

All possible 2-digit numbers formed by the digits 3, 7 and 9, when repetition of digits is not allowed are;

Starting with 3:

37

39

Starting with 7:

73

79

Starting with 9:

93

97

Hence, the possible 2-digit numbers are 37, 39, 73, 79, 93, 97.

Question 17(i)

Write all possible 3-digit numbers that can be formed by the digits 1, 3 and 7, using each digit only once in each number.

Answer

Starting with 1:

137

173

Starting with 3:

317

371

Starting with 7:

713

731

Hence, the possible 3-digit numbers are 137, 173, 317, 371, 713 and 731.

Question 17(ii)

Write all possible 3-digit numbers that can be formed by the digits 9, 2 and 0, using each digit only once in each number.

Answer

When forming 3-digit numbers using the digits 9, 2, and 0, with each digit used only once, we must remember that a 3-digit number cannot start with 0.

If the hundreds digit is 9 : the remaining digits are 2 and 0.

Possible numbers: 920, 902

If the hundreds digit is 2 : the remaining digits are 9 and 0.

Possible numbers: 290, 209

Hence, the possible 3-digit numbers are 920, 902, 290, 209.

Question 18(i)

Write the smallest 4-digit number that can be formed by the digits 0, 1, 3 and 6, using each digit only once.

Answer

The first digit of a 4-digit number cannot be 0. So, the smallest available non-zero digit is 1.

Thousands place: 1

The remaining digits are 0, 3, and 6. To make the number as small as possible, arrange these remaining digits in ascending order: 0, 3, 6.

Hundreds place: 0

Tens place: 3

Units place: 6

Combining all the data, the smallest 4-digit number is 1036.

Hence, the smallest 4-digit number is 1036.

Question 18(ii)

Write the greatest 4-digit number that can be formed by the digits 0, 2, 7 and 5, using each digit only once.

Answer

The given digits are: 0, 2, 7, 5.

Arranging them in descending order:

Largest digit: 7 (for the thousands place)

Next largest: 5 (for the hundreds place)

Next largest: 2 (for the tens place)

Smallest digit: 0 (for the units place)

Hence, the greatest 4-digit number that can be formed is 7520.

Question 19

Write the smallest 4-digit number of four different digits.

Answer

The digits available are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.

Thousands digit: The smallest digit is 0, but a number cannot start with 0 if it's meant to be a 4-digit number. So, the smallest non-zero digit, which is 1, must be in the thousands place.

Current digits used: {1}

Hundreds digit: Now that 1 is used, the smallest remaining digit available is 0.

Current digits used: {1, 0}

Tens digit: With 1 and 0 used, the next smallest digit available is 2.

Current digits used: {1, 0, 2}

Units digit: With 1, 0, and 2 used, the next smallest digit available is 3.

Current digits used: {1, 0, 2, 3}

Combining these digits in order, the smallest 4-digit number with four different digits is 1023.

Hence, the smallest 4-digit number with four different digits is 1,023.

Question 20

Write the greatest 4-digit number of four different digits.

Answer

The digits available are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.

Thousands digit: The largest digit is 9.

Current digits used: {9}

Hundreds digit: From the remaining digits, the next largest is 8.

Current digits used: {9, 8}

Tens digit: From the remaining digits, the next largest is 7.

Current digits used: {9, 8, 7}

Units digit: From the remaining digits, the next largest is 6.

Current digits used: {9, 8, 7, 6}

Combining these digits in order, the greatest 4-digit number with four different digits is 9876.

Hence, the greatest 4-digit number with four different digits is 9,876.

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