Tuesday Teaching Tip - Mental Math Stategies

Students may not have all facts memorized, but they should have strategies to solve these problems.

Here are some examples of mental-math strategies for addition:

1.  Counting On - Students start with a number and count on 1, 2, 3. For example, if the question is 5 + 2, students count 5, 6, 7. Note: This strategy is only useful for adding 1, 2, or 3.

2.  Make a Ten - Students make combinations that equal 10. Then they extend to make combinations that are multiples of 10. Examples: 6 + 4 = 10 extends to 76 + 4 = 80. This can then be extended to 10 + 4 = 14 or 50 + 8 = 58.

3.  Use Doubles - The first fact combinations students often learn are doubles. Examples:
2 + 2 =
3 + 3 =
8 + 8 =

4.  Think +10 for +9 -  Those 9s are such difficult facts!  But, adding 10 to a number is easy.  So, when I see 9 + 6, I can think 10 + 6 and then just subtract 1.

Here are some examples of mental-math strategies for subtraction:

1.  Counting Back - Students start with a number and count backwards. If the question is 5 – 2, students count 5, 4, 3. Note: This strategy is only useful for subtracting 1, 2, or 3.

2.  Counting Up - Students start with a number being subtracted and count up to the number from which it is being subtracted. For example, for the question 9 – 7, students can count 8, 9.

3.  Using Doubles - For the question 13 – 6 = ?, students think addition using doubles. For example, 6 + 6 = 12, then add-on 1 to make 13, so 6 + 1 = 7.

4.  Make Ten and Then Some - Given a subtraction question such as 14 – 8 = ?, students start with the part (8), add-on to make 10 (i.e., 8 + 2), then add-on from 10 to make 14 (10 + 4). Then the students add the numbers they added-on to make 14 (4 + 2 = 6).