Third Grade Addition Fact Strategies
Plus Zero “Zero Mirror” – Add 0 to a number and the number stays the same.
(Identity Property of Addition)
Example: 8
+0=8
Count Up – Count Up when adding on small numbers such as 1,2,3
Turn Around “Switcheroos” (Commutative Property) – Add numbers in any order and the total
stays the same.
Example: 3
+1=4
1+3=4
Doubles – Add the number to itself and that number doubles.
Example: 2
+2=4
Doubles Plus One “Neighbors” - Double the number and add one more. (The two addends are
neighbors on the number line.
Example: 2
+ 3 is the same as 2 + 2 + 1
Tens Partners “Make a Ten” – There are six sets of number pairs that make 10.
Example:
10 + 0 = 10
7 + 3 = 10
9 + 1 = 10
6 + 4 = 10
Plus Ten – Show students relationships using hundreds board. When
8 + 2 = 10
5 + 5 = 10
10 is added to a number, the
tens place digit increases by 1. Think of a hundreds board, going down one row.
Example: 30
+ 10 = 40
Plus Nine “Nifty Nines” – See 9 think or make 10. To add 9 to a number, add 10 instead and jump
back one. Using a number line, you can show students the visual of why this works.
Example: 6
+ 9 Think 6 + 10 – 1
OR
To add 9 to a number, make the 9 a 10 by reducing the other addend by 1. (10 frames)
Example: 9
+ 4 Make 10 + 3
Extension Strategies (to be taught AFTER above strategies are mastered when students are
developmentally ready in number sense.)
Doubles Plus Two - Double the number and add two more.
Example: 5
+ 7 is the same as 5 + 5 and 2 more or 12
Plus Eight – See 8 think or make 10. To add 8 to a number, add 10 instead and jump
back two. Using a number line, you can show students the visual of why this works.
Example: 6
+ 8 Think 6 + 10 – 2
OR
To add 8 to a number, make the 8 a 10 by reducing the other addend by 2. Ten frames
Work great to how this visually.
Example: 8
+ 4 Make 10 + 2
Add in Small Steps - Split the smaller number into two parts (this is called decomposing a number)
so that you can add to a multiple of 10.
Example: 26
+7=?
1. The Tens Partner for 26 is 4.
2. Split the smaller addend, 7, into (4
3.
4.
+ 3).
Add the Tens Partners Numbers 26 + 4 = 30.
Then add the remaining number 30 + 3 = 33
Hidden Facts – Finding tens partners and doubles hidden within problems can make them easier to
solve.
Hidden Tens Partners
Hidden Doubles
8 + 6 = (8 + 2) + 4
6 + 8 = (6 + 6) + 2
= 10 + 4
= 12 + 2
= 14
= 14
Plus 20 – When you add 20 to a number, the tens digit increases by 2.
Plus 19, Think 20 – For Plus 19, add 20 then subtract 1.
Plus 99, Think 100 – For Plus 99, add 100 then subtract 1.
Third Grade Subtraction Fact Strategies
Think Addition - Remind students of the relationship between addition and subtraction. These are
the fact family members from the addition facts they know.
Example: 13
–6=
so think
+ 6 = 13
Minus Zero “Zero Mirror” – Subtract 0 from a number and the number stays the same.
Example: 8
-0=8
Number Minus Itself “Numbers the Same” - Subtract a number from itself and the result is
I use the rhyme “If the numbers are the same, zero’s the name.”
Example: 8
0.
-8=0
Count Back – Count back to take away small numbers such as 1, 2 or 3. Use a number line to
show students the relationship and visual of what they are doing.
Example: 9
– 2 = 7 Start at 9 and count back 2.
Count Up - Count Up to find the difference when the numbers are close together.
Example:
11 – 9 = 2 Count up from 9 to 11.
Doubles – If you know the addition doubles, then you know the related subtraction fact.
Example: 2
+ 2 = 4 so 4 – 2 = 2
Tens Partners “Make a Ten” – If you know the six sets of number pairs that make 10, then you
know the related subtraction facts. This is a great opportunity to use ten frames to show
visual.
Example:
9 + 1 = 10 so 10 – 1 = 9
Minus Ten – Show students relationships using hundreds board. When
10 is subtracted from a
number, the tens place digit decreases by 1. Think of a hundreds board, going up one
row.
Example: 30
- 10 = 20
Minus Nine “Nifty Nines” – Remember that 9 is just one away from 10. See 9 think or make 10.
Example: 12
Example: 12
- 9 Think 12 - 10 + 1
-9
OR
Think
13 - 10
Extension Strategies (to be taught AFTER above strategies are mastered when students are
developmentally ready in number sense.)
Minus Eight – Remember that 8 is just two away from 10. See 8 think or make 10.
Example: 15
- 8 Think 15 - 10 + 2
OR
Example: 15
- 8 Think 17 - 10
Subtract In Small Steps – Split the number being subtracted into two parts. (This is called
decomposing numbers) so that you can subtract to 10 or a multiple of 10.
Example:
24 – 7 = ?
– 4 = 20
2. So split the 7 into 4 and 3
1. 24
3. Then apply the Tens Partners to subtract
4. 20
3 from 20.
– 3 = 17
Minus 20 - When you subtract 20, the tens place digit decreases by 2.
Minus 19 – Subtract 20 then add 1.
Minus 99 – Subtract 100 then add 1.