Information for Parents – Grade 3 Mental Math Strategies
Basic addition and subtraction facts to 18
**by the end of grade 2, students should be able to apply mental mathematics strategies, such
as: using doubles; making 10; one more, one less; two more, two less; addition for subtraction
to determine basic addition facts to 18 and related subtraction facts.
To help your child:
Skip Counting:
Practice skip counting with your child from 0 to 100 counting by 2s, 5s and 10s. Skip count
forward and backward, using starting points that are multiples of 2, 5 and 10. For example,
count backwards by 2’s from 32, forwards by 5’s from 25, backwards by 10’s starting at 80.
Addition strategies:

Start with the doubles and make sure they know them quickly and accurately: 2+2=4,
6+6=12, 8+8=16, etc.

Next, work on doubles plus one, then doubles plus two:
For example: 7 + 8 – They should know 7+7=14, so simply add one more and get 15.
6 + 8 – They should know 6+6=12, so add two more and get 14.

Partner numbers to ten: 5+5, 6+4, 7+3, 8+2, 9+1

Other partner numbers to 100 : 25+75, 50+50, 30+70, 55+45, 65 + 35
Subtraction strategies:

Count back if the number is small: 12 – 3, say “11, 10, 9. I counted back 3 and landed at
9, so the difference is 9”.

Count on if the numbers are close: 13 – 9, say “10, 11, 12, 13, I added on 4, so the
difference is 4”.

Think addition! Many students find that turning the subtraction fact into an addition fact
makes it easier.
For example, 16 – 9 think 9 + what? = 16. “ I know 9 + 7 = 16, so my difference is 7
Mental Addition Estimation Strategies (with larger numbers):
**students are required in grade 2 to show how they would estimate adding two digit numbers
mentally. Below are some mental addition strategies:
Rounding to 10 :
When estimating, 46 + 35 may be thought of as 50 + 35 instead.
Think 46 is closer to 50 than to 40. Therefore, the sum of 46 + 35 is about 85.
Front-end Addition (adding left to right) :
Add the tens first and then the ones.
Ex. 44 + 33 = ?
Think 40 + 30 and 4 + 3 = 77, or you can also say it without the plus in between,
40…70…74…77.
Estimating Combinations :
Use both strategies - Rounding to 10 AND Front-End Method.
Ex. 38 + 27 = ?
Think 38 is closer to 40, then I have 40 + 27 is equal to 40…60…67