Subtraction Strategies
1. Minus Zero - Subtract 0 from a number and the number stays the same. (8-0=0)
2. A Number Minus Itself - Subtract a number from itself and the result is 0. (8-8=0)
3. Count Back -1, -2, -3 - Count back to take away small numbers, such as 1, 2, or 3. (17-1=16 17-2=15 17-3=14)
4. Count Up - Count up to find the difference when the numbers are close together. (17-15 = 2 Count up two from 15 to 17).
5. Think Addition - To subtract, think of the related addition fact. (8+6=14 so 14-6=8)
6. Tens Partners - If you know the Tens Partners, then you know the related subtraction facts. (7+3=10 so 10-7=3)
7. Doubles - If you know the addition doubles, then you know the related subtraction facts. (6+6=12 so 12-6=6)
8. Minus Ten - Subtract 10 and the tens-place digit decreases by one, while the ones-place digit stays the same.
9. Minus Nine - Remember that 9 is just one away from 10. Two common approaches are:
See 9. Think 10 - Subtract 10 and add 1.
(See 12-9. Think 12-10+1)
or
See 9. Make 10 - Increase each number by one.
(Turn 12-9 into 13-10)
