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## Karnataka State Syllabus Class 5 Maths Chapter 3 Mental Arithmetic

### KSEEB Class 5 Maths Mental Arithmetic Revision Exercise

I. Round off each of the following numbers to nearest thousands place:

1. 7,547

7,547 lie between 7000 and 8000

Replace by zero

2. 3,469

3,469 lie between 2000 and 3000

Replace by zero

3. 15,238

15,038

Replace by zero

4. 32,658

32,658

Replace by zero

II. Round off each of the following numbers to nearest ten thousands place:

1. 26,674

26,674

Replace to zero

2. 32,464

32,464

Replace to zero

3. 46,379

46,379

Replace to zero

4. 53,668

53,668

Replace to zero

III. Estimate sum of the following by rounding off to nearest thousands place:

1. 42,125 + 35,637

42,125 is rounded off to nearest thousand – 42,000

35,637 is rounded off to nearest thousand – 36,000

Estimate sum is 78,000

Verification by actual addition – 42125

2. 54,837 + 41,354

54,837 is rounded off to nearest thousand – 55,000

41,354 is rounded offto nearest thousand – 41,000

Estimate sum is 96,000

Verification by actual addition

3. 33,231 + 20,097

33,321 is rounded off to nearest thousand – 33,000

20,097 is rounded off to nearest thousand – 20,000

Estimate sum is 53,000

Verification by actual addition

4. 47,463 + 41,541

47,463 is rounded off to nearest thousand – 47,000

41,541 is rounded off to nearest thousand – 42,000

Estimate sum is 89,000

Verification by actual addition

IV. Estimate the sum of the following by rounding off to nearest ten thousands place:

1. 56,256 + 24,872

56,256 is rounded off to nearest ten thousand – 55,000

24,872 is rounded off to nearest ten thousand – 25,000

Estimate sum is 80,000

Verification by actual addition

2. 47,671 + 28,745

47,671 is rounded off to nearest ten thousand – 50,000

28,745 is rounded off to nearest ten thousand – 30,000

Estimate sum is 80,000

Verification by actual addition

3. 32,184 + 45,138

32,184 is rounded off to nearest ten thousand – 30,000

45,138 is rounded off to nearest ten thousand – 50,000

Estimate, sum is 80,000

Verification by actual addition

4. 15,025 + 40,165

15,025 is rounded off to nearest ten thousand – 20,000

40,165 is rounded off to nearest ten thousand – 40,000

Estimate sum is 60,000

Detailed Steps to Round to Nearest Hundredth by Hand ·

V. Estimate the difference of the following by rounding off to nearest thousands place:

1. 65,487 – 46,502

65,487 is rounded off to nearest ten thousand – 64,000

46,502 is rounded off to nearest ten thousand – 46,000

Estimate sum is 18,000

Verification by actual substruction

2. 45,630 – 32,148

45,630 is rounded off to nearest ten thousand – 44,000

32,148 is rounded off to nearest ten thousand – 30,000

Estimate sum is 14,000

Verification by actual substruction

3. 57,146 – 25,472

57,146 is rounded off to nearest ten thousand – 56,000

25,472 is rounded off to nearest ten thousand – 24,000

Estimate sum is 32,000

Verification by actual substraction

4. 60,046 – 15,247

60,046 is rounded off to nearest ten thousand – 60,000

15,247 is rounded off to nearest ten thousand – 15,000

Estimate sum is 45,000

Verification by actual substraction

VI. Estimate the difference of thefolhming hy rounding off to nearest ten thousands place:

1. 51,689 – 34,685

51,689 is rounded off to nearest ten thousand – 50,000

34,685 is rounded off to nearest ten thousand – 30,000

Estimate sum is 20,000

Verification by actual substraction

2. 86,853 – 47,829

86,853 is rounded off to nearest ten thousand – 85,000

47,829 is rounded off to nearest ten thousand – 45,000

Estimate difference is 40,000

Verification by actual substraction

3. 80,808 – 55,055

80,808 is rounded off to nearest ten thousand – 80,000

55,055 is rounded off to nearest ten thousand – 50,000

Estimate difference is 30,000

Verification by actual substractiori

4. 77,777 – 44,444

77,777 is rounded off to nearest ten thousand – 70,000

44,444 is rounded off to nearest ten thousand – 40,000

Estimate difference is 30,000

Verification by actual substraction

VII. Estimate the product of each of the following hy rounding off to its highest place:

1. 428 × 54

428 is rounded off to nearest hundred as 400

54 is rounded off to nearest ten as 50

Estimate product is 20,000

2. 878 × 46

876 is rounded off to nearest hundred as 900

46 is rounded off to nearest ten as 50

Verification by actual multiplication

Verification by actual multiplication

3. 5,476 × 11

5,476 is rounded off to nearest hundred as 5000

11 is rounded off to nearest ten as 10

Verification by actual multiplication

Verification by actual multiplication

4. 2,645 × 18

2,645 is rounded off to nearest hundred as 3000

18 is rounded off to nearest ten as 20

Verification by actual multiplication

Verification by actual multiplication

VIII. Estimate the quotient of each of the following hy rounding off to its highest place.

1. 398 ÷ 82

398 is rounded off to nearest hundred aS 400

82 is rounded off to nearest ten as ÷ 80

Estimate quotient \(\frac{800}{40}\) = 5

2. 786 ÷ 22

786 is rounded off to nearest hundred as 800

22 is rounded off to nearest ten as ÷ 20

Estimate quotient \(\frac{800}{20}\) = 40

3. 3,265 ÷ 58

3,265 is rounded off to nearest hundred as 3000

58 is rounded off to nearest ten as ÷ 60

Estimate quotient \(\frac{3000}{60}\) = 50

4. 7,687 ÷ 43

7,687 is rounded off to nearest hundred as 8000

43 is rounded off to nearest ten as ÷ 40

Estimate quotient \(\frac{8000}{40}\) = 200

IX. Solve the following problems.

Question 1.

A garment company stitched 16,783 shirts and 12,438 pants in a month. Estimate the total number of dresses stitched to the nearest ten thousands place.

Answer:

A garment company stitched shirts – 16,783

A garment company stitched pants – 12,438.

(To the nearest ten thousand place) – 20,000

(To the nearest ten thousand place) – 10,000

Question 2.

A news paper agent sells 36,721 papers in first month and 24,172 papers in sec¬ond month. Estimate the decrease in sale of the newspaper in second month to the nearest ten thousands place.

Answer:

In first month a news paper agents sells – 36,721

In Second month a news paper agents sells – 24,172

(To the nearest ten thousand place)

first month – 40,000

Second month – 20,000

The estimated substraction of sale of the newspaper 20,000

Question 3.

A train can cover 225 km in one hour. Estimate the distance covered in a day to the highest place.

Answer:

A train can cover 225 Km in 1 hour

The distance covered in a day = 24 hours

(To the highest place) 200

Question 4.

A carpenter earned Rs. 18,634 during the month of November and Rs. 32,645 in December. Estimate how much more he earned in December to the nearest ten thousands place.

Answer:

A carpet earned in november – 18,634

A carpet earned in december – 32,645

(To the nearest ten thousand place)