Topic 2 Review!

Mental Math (Addition)

100

Find the sum using mental math:

43 + 4

What is:

40 + 3 + 4  = 47

200

Find the sum using mental math:

50 + 42

What is:

50 + 40 + 2  = 92

300

Find the sum using mental math:

35 + 26

What is:

35 + 20 + 6  = 61

or 

35 + 20 + 5 + 1  = 61

400

Find the sum using mental math:

5 + 38

What is:

5 + 30 + 8  = 43

or

5 + 30 + 5 + 3  = 43

500

Find the sum using mental math:

71 + 14

What is:

70 + 1 + 10 + 4  = 85

or

70 + 10 + 5  = 85

Mental Math (Subtraction)

100

Find the difference using mental math:

52 - 9

What is:

53 - 10 (Add 1 to each number)

53 - 10 = 43

200

Find the difference using mental math:

28 - 19

What is:

29 - 20 (Add 1 to each number)

29 - 20 = 9

300

Find the difference using mental math:

31 - 5

What is:

30 - 4 (Take 1 away from each number)

30 - 4 = 26

400

Find the difference using mental math:

97 - 14

What is:

100 - 17 (Add 3 to each number)

100 - 17 = 83

500

Find the difference using mental math:

73 - 39

What is:

74 - 40 (Add 1 to each number)

74 - 40 = 34

Estimating Sums

100

Which of the following ways shows how to estimate the sum of 365 + 212 by rounding to the nearest ten?

A) 300 + 200

B) 370 +210

C) 360 + 210

D) 400 + 200

What is:

B) 370 + 210

200

Round to the nearest ten to estimate:

18 + 43

What is:

20 + 40 = 60

300

Round to the nearest hundred to estimate:

403 + 179

What is:

400 + 200 = 600

400

Alex bought 118 Pokemon cards. His sister gave him 79 more. About how many Pokemon cards does Alex have now? Round to the nearest ten to estimate.

What is:

120 + 80 = 200

500

Use compatible numbers to estimate:

539 + 399

What is:

540 + 400 = 940

Estimating Differences

100

Which of the following ways shows how to estimate the sum of 542 - 408 by rounding to the nearest ten?

A) 500 - 400

B) 500 - 410

C) 540 - 410

D) 540 + 410

What is:

C) 540 - 410

200

Round to the nearest ten to estimate:

86 - 38

What is:

90 - 40 = 50

300

Round to the nearest hundred to estimate:

286 - 175

What is:

300 - 200 = 100

400

Jen drove 256 miles last week. This week she drove 532 miles. About how many more miles did Jen drive this week compared to last week? Find by rounding to the nearest ten.

What is:

530 - 260 = 270

500

Use compatible numbers to estimate:

361 - 117

What is:

360 - 120 = 240