Use counting back to subtract

Subtraction within 20 can be understood as removing a quantity from a starting amount: begin at the minuend and count backward one number for each unit in the subtrahend, with the endpoint representing the difference. A number line makes the starting point, direction, and number of steps visible and helps prevent counting the starting number as a step; this understanding does not extend here to larger numbers, multi-digit subtraction, or formal algorithms.

Detailed Explanation: Use counting back to subtract

Subtraction means taking away. To subtract by counting back:

Start at the first number.
Count backward one number for each number you subtract.
The number where you stop is the answer.

Example: Find $13-4$ .

Start at $13$ on a number line. Count back $4$ steps:

13 \rightarrow 12 \rightarrow 11 \rightarrow 10 \rightarrow 9

The four steps are:

Step 1: $13$ to $12$
Step 2: $12$ to $11$
Step 3: $11$ to $10$
Step 4: $10$ to $9$

You stop at $9$ , so:

13-4=9

Remember: Do not count $13$ as the first step. Start at $13$ , then move backward.

Learn by doing: Use counting back to subtract

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Number Line - Subtraction Positive Integers, Movement Image to Equation

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Use counting back to subtract

Detailed Explanation: Use counting back to subtract

Learn by doing: Use counting back to subtract

Practice with unlimited practice problems

Practice:

Number Line - Subtraction Positive Integers, Movement Image to Equation