Unit 6: Strategies to subtract fluently within 20

Regrouping

100

Solve 17-9=? by regrouping.

17-9=8

200

Solve 26-19=? by regrouping.

26-19=7

300

Brian's haircut takes 32 minutes. Ben's haircut takes 19 minutes. How many more minutes does Brian's haircut take than Ben's haircut? Solve by regrouping.

32-19=13

400

The barber has a box of 43 combs. He takes 26 combs out of the box. How many combs are still in the box? Solve by regrouing.

43-26=17

500

Ms. Becker has 78 treats for Lola. Lola hides 29 of the treats. How many bones are left for Ms. Becker to put away? 

78-29=49

Number line & Bar

100

Use a number line to solve! 17-8=?

17-8=9

200

Create a number line. Solve 17-11=?

17-11=6 

300

Create a number line. Solve 30-17=?

30-17=13

400

Create a number line. Solve 43-24=?

43-24=19

500

Create a number line. Solve 59-43=?

59-43=16

Decomposing

100

How can you decompose a number to subtract? 49-22=?

49-22=? 22= [20+2]

49-20=?

29-2=27

200

Solve 39-16=? by decomposing.

39-16=? 39-(10+6)=?

39-10=29

29-6=23

300

Solve 76-48=? by decomposing.

76-48=? 76-(40+8)=?

76-40=36

36-8=28

400

Solve 55-25=? by decomposing.

55-25=? 55-(20+5)=?

55-20=35

35-5=30

500

Solve 78-29=? by decomposing.

78-29=? 78-(20+9)=?

78-20=58

58-9=49

Adjusting

100

Solve 27-19=? by adjusting with friendly numbers.

27-19=?

+3 +3

30-22=8

OR

+1 +1

28-20=8

200

Solve 31-19=? by adjusting.

31-19=

-1 -1

30-18=12

OR

+1 +1

32-20=12

300

Solve 57-28=? by adjusting.

57-28=?

+3 +3

60-31=29

OR

+2 +2

59-30=29

400

Solve 79-31=? by adjusting.

79-31=?

+1 +1

80-32=48

OR

-1 -1

78-30=48

500

Solve 97-29=? by adjusting.

97-29=?

+3 +3

100-32=68

OR

-2 -2

95-27=68

Base Ten Short Hand

100

Solve 37-19=? by using base ten short hand.

37-19=18

200

Solve 48-39=? by using base ten short hand.

48-39=9

300

Solve 54-49=? by using base ten short hand.

54-49=5

400

Solve 68-39=? by using base ten short hand.

68-39=29

500

Solve 92-49=? by using base ten short hand.

92-49=43