Math Strategies and Other Practices for Addition and Subtraction - Grade 2
Strategy 1: Doubles Plus One or Minus One
• Looking for the “neighbors” or “near doubles”
Example: 6 + 7 = ___
Think of the double 6 + 6 = 12
• You change the second number from a 7 to a 6 to make the numbers the same
(doubles).
You then add one more to twelve to get the answer or 13.
!
or
Think of the double of 7 + 7 = 14
• You change the first number from a 6 to a 7 to make the numbers the same
(doubles).
You then must take one away from fourteen to make 13, as you added an extra number
on to the front number.
Strategy 2: Balancing Out Numbers (Sharing to Make Doubles)
• Used for numbers that are 2 apart (for example, 5+7) so that if the larger number
would give one to the smaller number, then the numbers would be balanced (shared
equally). Think of it as a two-pan balance scale - The numbers need to balance out
and be equal or even. The piles would be even and the numbers are converted into
doubles.
Example: 5 + 7 = ___
The larger number (7) will give one to the smaller number (5), which means 5 becomes
6 and since 7 gave one away, it is also 6.
5 + 7 =
(5 + 1) + (7 - 1) =
6
+ 6 =
Therefore, we now have 6 + 6 = ____ which is the same as 5 + 7, which equals 12.
Strategy 3: Doubles Plus and Minus Two
• Similar to doubles plus or minus one except that you add or subtract two after using
the double for either the lowest or highest addend.
Example: 6 + 8 = ___
This could be solved as 6 + 6 + 2 = 14 or as 8 + 8 - 2 =14.
In the first solution, the 6 is used for the double, therefore we know we need to split the
8 up into 6 (to make the other part of the double) plus two more to make the number
sentence balance out.
6 + 8 becomes
6 + (6 + 2) =
In the second solution, the 8 (higher addend) is used for the double, therefore we know
we need to convert the first part into an 8 (to make the other part of the double) minus
two from it to make the number sentence balance out, since we made it bigger in the
front.
6 + 8 becomes...
8 + 6 .....as order in addition does not matter!
8 + (8 - 2) =
Strategy 4: Making Ten
• This strategy is particularly useful for equations (number sentences) in which one of
the addends has a 7, 8, or 9 in the ones place.
Example: 9 + 6 = ___
We need to know that 6 can be broken down into two parts (5 and 1) and we also need
to know that 10 is 9 + 1. In other words, think 9 + 6 as “9 and 1 (from the 6) which
makes 10, and 10 + 5 (the rest of the 6) is 15.”
(Steps shown below)
Join the 1 from the (5 and 1) with the 9 to make 10.
Finally, add the 10 to the 5 for a total of 15.
(See steps below)
9
9
(9 + 1)
10
+
+
+
+
6
(5 + 1)
5
5
Therefore, we have 10 + 5 = 15
Example: 28 + 8 = ___
To add 28 + 8, think, “28 and 2 (from the 8) is 30, and 30 + 6 (the rest of the 8) is 36”.
Therefore, 28 + 8 = 36.
Sample addition problem and strategy:
Sadie had read part of her new book before the class left the library. That night she read
another 8 pages. Now she is on page 17. How many pages of her book had she read in the
library?
Subtraction Equation
17 - 8 = 9
Helpful Addition Fact
9 + 8 = 17
Sentence Answer to the Problem
Personal Strategy Used for Addition Fact
Sadie read 9 pages of her new book
during library period.
*Please note that these are strategies
we are working on and will continue to develop and
work on throughout our unit. This is a guide to help with
at-home activities and in supporting your child with
addition and subtraction strategies and implementation
throughout our math units.
Doubles Plus One
8+8+1=
16 + 1 = 17