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In this pdf, you will learn to estimate sums and differences using the method of rounding the number to the leading digit.

1.
Estimating sums and differences ✩

Round the numbers to the leading digit. Estimate the sum or difference.

3,576 → 4,000 198,248 → 200,000

+ 1,307 → +1,000 – 116,431 → –1,00,000

is about 5,000 is about 100,000

Round the numbers to the leading digit. Estimate the sum or difference.

685 → 21,481 → 7,834 →

+ 489 → – 12,500 → + 3,106 →

is about is about is about

682,778 → 58,499 → 902,276 →

+ 130,001 → – 22,135 → – 615,999 →

is about is about is about

46,801 → 9,734 → 65,606 →

+ 34,700 → – 8,306 → + 85,943 →

is about is about is about

5,218 → 745 → 337,297 →

– 3,673 → + 451 → – 168,931 →

is about is about is about

Write < or > for each problem.

329 + 495 800 11,569 – 6,146 6,000

563 – 317 300 8,193 – 6,668 1,000

41,924 – 12,445 50,000 634,577 + 192,556 800,000

18,885 + 12,691 30,000 713,096 – 321,667 400,000

© Dorling Kindersley Limited [2010]

Round the numbers to the leading digit. Estimate the sum or difference.

3,576 → 4,000 198,248 → 200,000

+ 1,307 → +1,000 – 116,431 → –1,00,000

is about 5,000 is about 100,000

Round the numbers to the leading digit. Estimate the sum or difference.

685 → 21,481 → 7,834 →

+ 489 → – 12,500 → + 3,106 →

is about is about is about

682,778 → 58,499 → 902,276 →

+ 130,001 → – 22,135 → – 615,999 →

is about is about is about

46,801 → 9,734 → 65,606 →

+ 34,700 → – 8,306 → + 85,943 →

is about is about is about

5,218 → 745 → 337,297 →

– 3,673 → + 451 → – 168,931 →

is about is about is about

Write < or > for each problem.

329 + 495 800 11,569 – 6,146 6,000

563 – 317 300 8,193 – 6,668 1,000

41,924 – 12,445 50,000 634,577 + 192,556 800,000

18,885 + 12,691 30,000 713,096 – 321,667 400,000

© Dorling Kindersley Limited [2010]

2.
8 4 0 2 8 4

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6

3

1

3

4

0

1

9

Estimating sums and differences ✩ 1

7 1

2

3

Round the numbers to the leading digit. Estimate the sum or difference. 2 4

5

6

3,576 → 4,000 198,248 → 200,000

0

7

+ 1,307 → + 1,000 – 116,431 → – 100,000 8

is about 5,000 is about 100,000 9

7 10

11

Round the numbers to the leading digit. Estimate the sum or difference. 6 12

13

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685 → 700 21,481 → 20,000 7,834 → 8,000 15

8

+ 489 → + 500 – 12,500 → – 10,000 + 3,106 → + 3,000 16

is about 1,200 is about 10,000 is about 11,000 17

18

19

682,778 → 700,000

+ 130,001 → + 100,000

58,499 → 60,000

– 22,135 → – 20,000

902,276 → 900,000

– 615,999 → – 600,000

1 20

21

is about 800,000 is about 40,000 is about 300,000 22

3

23

24

46,801 → 50,000 9,734 → 10,000 65,606 → 70,000

9 25

+ 34,700 → + 30,000 – 8,306 → – 8,000 + 85,943 → + 90,000

5 26

27

is about 80,000 is about 2,000 is about 160,000

28

29

5,218 →

– 3,673 →

5,000

– 4,000

745 →

+ 451 →

700

+ 500

337,297 → 300,000

– 168,931 → – 200,000

4 30

31

32

is about 1,000 is about 1,200 is about 100,000

9 33

34

35

2

Write < or > for each problem. 36

37

329 + 495 > 800 11,569 – 6,146 < 6,000 3 38

39

40

563 – 317 < 300 8,193 – 6,668 > 1,000

41

41,924 – 12,445 < 50,000 634,577 + 192,556 > 800,000

5 42

43

6

44

45

46

18,885 + 12,691 > 30,000 713,096 – 321,667 < 400,000

47

9 48

2 7 2

115

7

8

3

6 carefully if the

9

In section 2, children need to think about their estimates more

0

4

3

estimate is very close to the number on the right side of the equation. Have

them look at the numbers in the next place to the right to adjust their estimates

up or down.

© Dorling Kindersley Limited [2010]

2

6

3

1

3

4

0

1

9

Estimating sums and differences ✩ 1

7 1

2

3

Round the numbers to the leading digit. Estimate the sum or difference. 2 4

5

6

3,576 → 4,000 198,248 → 200,000

0

7

+ 1,307 → + 1,000 – 116,431 → – 100,000 8

is about 5,000 is about 100,000 9

7 10

11

Round the numbers to the leading digit. Estimate the sum or difference. 6 12

13

14

685 → 700 21,481 → 20,000 7,834 → 8,000 15

8

+ 489 → + 500 – 12,500 → – 10,000 + 3,106 → + 3,000 16

is about 1,200 is about 10,000 is about 11,000 17

18

19

682,778 → 700,000

+ 130,001 → + 100,000

58,499 → 60,000

– 22,135 → – 20,000

902,276 → 900,000

– 615,999 → – 600,000

1 20

21

is about 800,000 is about 40,000 is about 300,000 22

3

23

24

46,801 → 50,000 9,734 → 10,000 65,606 → 70,000

9 25

+ 34,700 → + 30,000 – 8,306 → – 8,000 + 85,943 → + 90,000

5 26

27

is about 80,000 is about 2,000 is about 160,000

28

29

5,218 →

– 3,673 →

5,000

– 4,000

745 →

+ 451 →

700

+ 500

337,297 → 300,000

– 168,931 → – 200,000

4 30

31

32

is about 1,000 is about 1,200 is about 100,000

9 33

34

35

2

Write < or > for each problem. 36

37

329 + 495 > 800 11,569 – 6,146 < 6,000 3 38

39

40

563 – 317 < 300 8,193 – 6,668 > 1,000

41

41,924 – 12,445 < 50,000 634,577 + 192,556 > 800,000

5 42

43

6

44

45

46

18,885 + 12,691 > 30,000 713,096 – 321,667 < 400,000

47

9 48

2 7 2

115

7

8

3

6 carefully if the

9

In section 2, children need to think about their estimates more

0

4

3

estimate is very close to the number on the right side of the equation. Have

them look at the numbers in the next place to the right to adjust their estimates

up or down.

© Dorling Kindersley Limited [2010]