Adding
Subtraction
Fast Facts
Math Detectives
100

24 + 13

37

100

46 − 12

34

100
8+7

15

100

True or False? 34 + 18 = 52.

True

200

36+27

63

200

52 − 28

24

200

14 − 6

8

200

A student solves 42 − 17 = 35. What did the student do wrong? What is the correct answer?

The student did not regroup correctly. The correct answer is 25.

300

48 + 35

83

300

71 − 36

35

300

9 + 6

15

300

Does 56 + 27 require regrouping? Explain why.

Yes. 6 + 7 = 13 ones, so trade 10 ones for 1 ten.

400

167 + 25

192

400

153 − 27

126

400

8 + ___ = 14

6

400

There are 63 books on a shelf. Students check out 28 books. How many books are left?

35 books

500

278 + 146

424

500

402 − 168

234

500

6 + 7 + 4

17

500

A student solves 38 + 25 = 513. Explain the mistake and find the correct answer.

The student did not regroup the 13 ones. Trade 10 ones for 1 ten. The correct answer is 63.