Definition
Count back
Count back means start at a number and say earlier numbers, usually one less each time.
What it means
Put your finger on the starting number. Each count moves one step lower: 9, 8, 7. When you use count back for subtraction, make one backward move for each one being taken away.
Remember it
Start on the number; every spoken number is one step back.
Example
To work out 12 − 4, start on 12 and count four backward steps: 11, 10, 9, 8. The result is 8.
Watch for
For 9 − 3, saying 9, 8, 7 stops too soon. The 9 is the starting point, so the three backward counts are 8, 7, 6.
Common mix-up
Do not count the starting number as the first step. Count the moves away from it.
Exact meaning
To count back is to continue a counting sequence in descending order from a known starting number, usually moving back by one for each count. In subtraction, the starting number is the starting point, not the first backward step.