1. Estimate Sums
and Differences

2. Round
Round- to find the nearest value of a number based on a given place value.

3. Find your number. Look right next door. 4 or less, just ignore.
Rounding
Memorize this Poem
Find your number.
Look right next door.
4 or less, just ignore.
5 or more, add 1 more.

4. Round to the nearest tens place
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Rounding
Round to the nearest tens place 3 7
Look right next door.
Find your number.

5. Round to the nearest tens place
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Step 3: If the number is four or less, then the circled number stays the same.
Step 4: If the number is 5 or greater than add 1 to the circled number.
Step 5: All numbers to the right of the circled number become zeros.
Rounding
Round to the nearest tens place 4 3 7
3 + 1 = 4
7 is not less than 4
5 or more, add 1 more.
4 or less, just ignore.

6. 37 rounded to the nearest tens place is
Number Line
37 rounded to the nearest tens place is 40 37 40 30
37 is closer to 40 on the number line.

7. Round to the nearest tens place
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Rounding
Round to the nearest tens place 5 2
Look right next door.
Find your number.

8. Round to the nearest tens place
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Step 3: If the number is four or less, then the circled number stays the same.
Step 4: All numbers to the right of the circled number become zeros.
Rounding
Round to the nearest tens place
Just Ignore! 5 2
2 is less than 4
4 or less, just ignore.

9. 52 rounded to the nearest tens place is
Number Line
52 rounded to the nearest tens place is 50 52 60 50
52 is closer to 50 on the number line.

10. Round to the nearest thousands place.
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Rounding
Round to the nearest thousands place. 7 , 4 6 3
Look right next door.
Find your number.

11. Round to the nearest thousands place.
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Step 3: If the number is four or less, then the circled number stays the same.
Step 4: All numbers to the right of the circled number become zeros.
Rounding
Round to the nearest thousands place. 7 , 4 6 3
Just Ignore!
4 = 4
4 or less, just ignore.

12. 7,463 rounded to the nearest thousands place is
Number Line
7,463 rounded to the nearest thousands place is
7,000
7,000
7,463
8,000
7,463 is closer to 7,000 on the number line.

13. Round to the nearest tenths place.
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Rounding
Round to the nearest tenths place. 5 . 6 8
Look right next door.
Find your number.

14. Round to the nearest tenths place.
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Step 3: If the number is four or less, then the circled number stays the same.
Step 4: If the number is 5 or greater than add 1 to the circled number.
Step 5: All numbers to the right of the circled number become zeros.
Rounding
Round to the nearest tenths place. 5 . 7 6 8
8 is not less than 4
6 + 1 = 7
5 or more, add 1 more.
4 or less, just ignore.

15. 5.68 rounded to the nearest tenths place is
Number Line
5.68 rounded to the nearest tenths place is
5.7
5.68
5.7
5.6
5.68 is closer to 5.7 on the number line.

16. Round to the nearest hundredths place.
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Rounding
Round to the nearest hundredths place. 6 . 4 5 8
Look right next door.
Find your number.

17. Round to the nearest hundredths place.
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Step 3: If the number is four or less, then the circled number stays the same.
Step 4: If the number is 5 or greater than add 1 to the circled number.
Step 5: All numbers to the right of the circled number become zeros.
Rounding
Round to the nearest hundredths place. 6 . 4 5 6 8
8 is not less than 4
5 + 1 = 6
5 or more, add 1 more.
4 or less, just ignore.

18. 6.458 rounded to the nearest hundredths place is
Number Line
6.458 rounded to the nearest hundredths place is
6.46
6.458
6.45
6.46
6.458 is closer to 6.46 on the number line.

19. Round to the nearest thousandths place.
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Rounding
Round to the nearest thousandths place. . 4 9 9 7
Look right next door.
Find your number.

20. . 4 5 9 9 7 +1 4 or less, just ignore. 5 or more, add 1 more. Rounding
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Step 3: If the number is four or less, then the circled number stays the same.
Step 4: If the number is 5 or greater than add 1 to the circled number.
Step 5: All numbers to the right of the circled number become zeros.
Rounding
Round to the nearest thousandths place. +1 . 4 5 9 9 7
10 thousandths = 1 hundredths. Time to regroup!
10 hundredths = 1 tenth. Time to regroup!
7 is not less than 4
4 + 1 = 5
9 + 1 = 10
9 + 1 = 10
5 or more, add 1 more.
4 or less, just ignore.

21. .4997 rounded to the nearest thousandths place is
Number Line
.4997 rounded to the nearest thousandths place is .5
.4997
.499 .5
.4997 is closer to .5 on the number line.

22. Round to the nearest dollar.
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Rounding
Round to the nearest dollar. $ 5 . 7 2
Look right next door.
Find your number.

23. Round to the nearest dollar.
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Step 3: If the number is four or less, then the circled number stays the same.
Step 4: If the number is 5 or greater than add 1 to the circled number.
Step 5: All numbers to the right of the circled number become zeros.
Rounding
Round to the nearest dollar. $ 5 6 . 7 2
7 is not less than 4
5 + 1 = 6
5 or more, add 1 more.
4 or less, just ignore.

24. $5.72 rounded to the nearest dollar is
Number Line
$5.72 rounded to the nearest dollar is
$6.00
$5.00
$5.72
$6.00
$5.72 is closer to $6.00 on the number line.

25. Round to the nearest ten cents.
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Rounding
Round to the nearest ten cents. $ 9 . 3 4
Look right next door.
Find your number.

26. Round to the nearest ten cents.
Step 1: Circle the digit in the place that you must round to.
Step 2: Draw an arrow to the place on the right.
Step 3: If the number is four or less, then the circled number stays the same.
Step 4: All numbers to the right of the circled number become zeros.
Rounding
Round to the nearest ten cents. $ 9 . 3 4
Just Ignore!
4 = 4
4 or less, just ignore.

27. $9.34 rounded to the nearest ten cents is
Number Line
$9.34 rounded to the nearest ten cents is
$9.30
$9.30
$9.34
$9.40
$9.34 is closer to $9.30 on the number line.

28. Your Turn! Round to the… …nearest ten 544 …nearest hundred 9,564
…nearest million ,897,876
…nearest thousand 5,389
…nearest hundred thousand ,900
…nearest ten cents $8.35
…nearest thousand 5,785,965
…nearest dollar $56.39
…nearest hundred ,987
540
9,600
13,000,000
5,000
200,000
$8.40
5,786,000
$56.00
936,000

29. Your Turn! Round to the… …nearest tenth 1.24 …nearest hundredth 12.765
12.77
0.43
0.4
8.6
2.9
156.8
3.53
0.9

30. Estimate- to find a number that is close to the exact answer.

31. Estimation When to use estimation… When an exact answer is not needed.
When you need to compute a problem quickly.
To check your work.

32. The actual answer is 616, so our estimation is pretty accurate.
Estimating Sums
The actual answer is 616, so our estimation is pretty accurate. 5 00 + 1 00 = 6
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round each addend to the hundreds place.
Step 3: Now you can add 500 and 100 mentally.
© 2007 M. Tallman

33. The actual answer is 5,773, so our estimation is pretty accurate
Estimating Sums
Rounding Tip: The lower the place, the more accurate the answer. However, if you round too low, your problem may be more difficult to solve. 5,
Rounding Tip: The higher the place, the easier your problem will be to solve. However, your answer may not be as accurate.
You could also
round 5,387 to
the hundreds place,
5,000 +
400 =
5,400
The actual answer is 5,773, so our estimation is pretty accurate
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round the first addend to the thousands place and the second addend to the hundreds place.
Step 3: Now you can add 5,000 and 400 mentally.
© 2007 M. Tallman

34. Estimating Sums 5,
You could also
round 5,387 to
the hundreds place,
5,000
5,400 +
400 =
5,400
5,800
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round the first addend to the thousands place and the second addend to the hundreds place.
Step 3: Now you can add 5,400 and 400 mentally.
© 2007 M. Tallman

35. The actual answer is 71,475, so our estimation is pretty accurate.
Estimating Sums
The actual answer is 71,475, so our estimation is pretty accurate.
44, ,578
40,000 +
30,000 =
70,000
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round each addend to the ten thousands place.
Step 3: Now you can add 40,000 and 30,000 mentally.
© 2007 M. Tallman

36. The actual answer is $15.42, so our estimation is pretty accurate.
Estimating Sums
The actual answer is $15.42, so our estimation is pretty accurate.
$ $6.75
$9.00 +
$7.00 =
$16.00
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round each addend to the nearest dollar.
Step 3: Now you can add $9.00 and $7.00, mentally.
© 2007 M. Tallman

37. The actual answer is 22.2, so our estimation is pretty accurate.
Estimating Sums
The actual answer is 22.2, so our estimation is pretty accurate. 17 + 5 = 22
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round each addend to the nearest whole number.
Step 3: Now you can add 17 and 5 mentally.
© 2007 M. Tallman

38. The actual answer is 12.5, so our estimation is pretty accurate.
Estimating Sums
The actual answer is 12.5, so our estimation is pretty accurate. 10 + 3 = 13
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round each addend to the nearest whole number.
Step 3: Now you can add 10 and 3 mentally.
© 2007 M. Tallman

39. The actual answer is 49.1, so our estimation is pretty accurate.
Estimating Sums
The actual answer is 49.1, so our estimation is pretty accurate. 43 + 6 = 49
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round each addend to the nearest whole number.
Step 3: Now you can add 43 and 6 mentally.
© 2007 M. Tallman

40. Your Turn!
Estimate Each Sum
1. $ $6.78
$20.00 +
$7.00 =
$27.00
500 +
700 =
1,200
100 +
500 =
600
4. 4,
5,000 +
600 =
5,600
© 2007 M. Tallman

41. Your Turn!
Estimate Each Sum 14 + 4 = 18 1 + 16 = 17
7. $ $102.5
$9.00 +
$103.00 =
$112.00
8. $ $28.70
$5.00 +
$29.00 =
$34.00
© 2007 M. Tallman

42. Your Turn!
Estimate Each Sum
9. $ $14.67
$3.00 +
$15.00 =
$18.00 6 + 33 = 39
11. $ $2.45
$30.00 +
$2.00 =
$32.00 + 13 = 13
© 2007 M. Tallman

43. Estimate
Differences
© 2007 M. Tallman

44. 496 - 112 500 - 100 = 400 Estimating Differences
The actual answer is 384, so our estimation is pretty accurate.
500 -
100 =
400
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round each number to the hundreds place.
Step 3: Now you can subtract 100 from 500, mentally.
© 2007 M. Tallman

45. 5,251 - 896 5,000 - 900 = 4,100 Estimating Differences
Rounding Tip: The lower the place, the more accurate the answer. However, if you round too low, your problem may be more difficult to solve. 5,
Rounding Tip: The higher the place, the easier your problem will be to solve. However, your answer may not be as accurate.
5,000 -
900 =
4,100
The actual answer is 4,355, so our estimation is pretty accurate
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round the first addend to the thousands place and the second addend to the hundreds place.
Step 3: Now you can subtract 900 from 5,000, mentally.
© 2007 M. Tallman

46. 52,187 - 18,978 50,000 - 20,000 = 30,000 Estimating Differences
The actual answer is 33,209, so our estimation is pretty accurate.
52, ,978
50,000 -
20,000 =
30,000
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round each addend to the ten thousands place.
Step 3: Now you can subtract 20,000 from 50,000, mentally.
© 2007 M. Tallman

47. $19.67 - $6.35 $20.00 - $6.00 = $14.00 Estimating Differences
The actual answer is $13.32, so our estimation is pretty accurate.
$ $6.35
$20.00 -
$6.00 =
$14.00
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round $19.67 to the nearest ten dollars. Round $6.35 to the nearest dollar.
Step 3: Now you can subtract $6.00 from $20.00, mentally.
© 2007 M. Tallman

48. 17.4 - 4.8 17 - 5 = 12 Estimating Differences
The actual answer is 12.6, so our estimation is pretty accurate. 17 - 5 = 12
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round each number to the nearest whole number.
Step 3: Now you can subtract 17 and 5 mentally.
© 2007 M. Tallman

49. 15.7 - 7.8 16 - 8 = 8 Estimating Differences
The actual answer is 7.9, so our estimation is pretty accurate. 16 - 8 = 8
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round each number to the nearest whole number.
Step 3: Now you can subtract 18 and 8 mentally.
© 2007 M. Tallman

50. 45.8 - 6.3 46 - 6 = 40 Estimating Differences
The actual answer is 39.5, so our estimation is pretty accurate. 46 - 6 = 40
Step 1: Rounding is always first. Decide which place to round to.
Step 2: Round each number to the nearest whole number.
Step 3: Now you can subtract 46 and 6 mentally.
© 2007 M. Tallman

51. Estimate Each Difference
Your Turn!
Estimate Each Difference
1. $ $6.78
$20.00 -
$7.00 =
$13.00
500 -
200 =
300
700 -
500 =
200
4. 4,
5,000 -
900 =
4,100
© 2007 M. Tallman

52. Estimate Each Difference
Your Turn!
Estimate Each Difference 14 - 4 = 10 10 - 6 = 4
7. $ $2.59
$9.00 -
$3.00 =
$6.00
8. $ $8.70
$15.00 -
$9.00 =
$6.00
© 2007 M. Tallman

53. Estimate Each Difference
Your Turn!
Estimate Each Difference
9. $ $14.67
$23.00 -
$15.00 =
$8.00 66 - 33 = 33
11. $ $2.45
$30.00 -
$2.00 =
$28.00 12 - 1 = 11
© 2007 M. Tallman

54. Points to Keep in Mind When Estimating
The higher the place is that you round to, the easier the estimation will be. Your answer may be less accurate though.
The lower the place that you round to, the more difficult your estimation will be. Your answer will be more accurate though.
Always ask yourself, “What makes the most sense?”.