1/15
00:00

M.1 Subtract by counting back - up to 20

Loading questions...

What does it mean to subtract by counting back?

Subtracting by counting back is a strategy where you start with the larger number and count backward to find the answer. This helps when subtracting small numbers, especially with facts up to 20.

Example:
  • Start with 9.
  • Subtract 3 by counting back: 8, 7, 6.
  • Answer: 9 βˆ’ 3 = 6.
Note

Always begin with the bigger number and count backward the smaller number of steps.

How can I identify when to count back?

You can use counting back when the numbers are small and the subtraction is easy to track on your fingers or in your head.

Examples:
  • 8 βˆ’ 2 β†’ count back two steps: 7, 6 β†’ answer is 6.
  • 12 βˆ’ 5 β†’ count back five steps: 11, 10, 9, 8, 7 β†’ answer is 7.
Note

If the number being subtracted is very small (like 1, 2, or 3), counting back is quick and reliable.

Using a number line to count back

A number line can help you see subtraction. Start at the bigger number and hop back the smaller number of steps.

Example:
  • Problem: 15 βˆ’ 4
  • Start at 15 on the number line.
  • Hop back 4 steps: 14, 13, 12, 11.
  • Answer: 15 βˆ’ 4 = 11.
Note

Using a number line is helpful if you lose track when counting in your head. It shows the jumps clearly.

Practice subtraction in sentences

It helps to think of subtraction in word problems. Counting back works well in real-life situations.

Examples:
  • β€œI had 7 apples. I ate 2. How many are left?” β†’ Count back 2 from 7 β†’ 5 apples.
  • β€œThere are 13 birds in a tree. 4 fly away. How many remain?” β†’ Count back 4 from 13 β†’ 9 birds.
Note

Always connect subtraction to real-world examples. It makes the strategy easier to understand and remember.