Mental Math Strategies

Doubles Plus One

100

If 3 + 3 = 6

Then 3 + 4 = ?

7

200

If 8 + 8 = 16

Then 8 + 9 = ?

17

300

Use doubles plus one to find the sum.

20 + 21 = ?

41

400

Use doubles plus one to find the sum.

40 + 41 = ?

81

500

Use doubles plus one to find the sum.

61 + 60 = ?

121

Doubles Minus One

100

If 4 + 4 = 8

Then 4 + 3 = ?

7

200

If 10 + 10 = 20

Then 10 + 9 = ?

19

300

Use doubles minus one to find the sum.

30 + 29 = ?

59

400

Use doubles minus one to find the sum.

50 + 49 = ?

99

500

Use doubles minus one to find the sum.

25 + 24 = ?

49

Doubles Missing Addend

100

4 + ____ = 9

5

200

7 + ____ = 15

8

300

20 + ____ = 39

19

400

30 + ____ = 59

29

500

25 + ____ = 51

26

Make a Nice Number

100

Make a nice number by adding an amount. Remember to take that amount away from the second number. Write the new addition sentence.

12 + 8

New addition sentence:

10 + 10

200

Make a nice number by adding an amount. Remember to take that amount away from the second number. Write the new addition sentence.

15 + 7

New addition sentence:

20 + 2 

OR

10 + 12

300

Make a nice number by adding an amount. Remember to take that amount away from the second number. Write the new addition sentence.

22 + 7

New addition sentence:

20 + 9

400

Make a nice number by adding an amount. Remember to take that amount away from the second number. Write the new addition sentence.

46 + 11

New addition sentence:

40 + 17

OR

50 + 7

500

Make a nice number by adding an amount. Remember to take that amount away from the second number. Write the new addition sentence.

57 + 14

New addition sentence:

50 + 21

OR

60 + 11

Make a Nice Number

100

Make a nice number by adding an amount. Remember to take that amount away from the second number. Write the new addition sentence.

14 + 7

New addition sentence:

10 + 11

OR

20 + 1

200

Make a nice number by adding an amount. Remember to take that amount away from the second number. Write the new addition sentence.

21 + 14

New addition sentence:

20 + 15

OR

30 + 5

300

Make a nice number by adding an amount. Remember to take that amount away from the second number. Write the new addition sentence.

34 + 8

New addition sentence:

30 + 12

OR

40 + 2

400

Make a nice number by adding an amount. Remember to take that amount away from the second number. Write the new addition sentence.

52 + 11

New addition sentence:

50 + 13

OR

60 + 3

500

Make a nice number by adding an amount. Remember to take that amount away from the second number. Write the new addition sentence.

83 + 8

New addition sentence:

80 + 11

OR

90 + 1