Recall subtraction facts within 20

This understanding includes accurate, efficient recall of subtraction facts with minuends up to 20 and nonnegative differences, including subtracting 0 and subtracting a number from itself. It connects subtraction to addition through inverse operations and part–whole relationships, enabling a fact such as $15-7=8$ to be interpreted as finding the missing part in $7+?=15$ ; larger-number computation and formal algorithms are not included.

Detailed Explanation: Recall subtraction facts within 20

Subtraction can be thought of as finding a missing part. Use addition to help:

15-7=?

Start with the number being subtracted: $7$ .
Ask, “What number added to $7$ makes $15$ ?”
Count up from $7$ to $15$ :

7+1=8,\quad 7+2=9,\quad \ldots,\quad 7+8=15

The missing number is $8$ , so:

15-7=8

Check your answer with addition:

7+8=15

So, the subtraction fact is correct. Remember that subtracting $0$ leaves a number the same, and subtracting a number from itself gives $0$ .

Learn by doing: Recall subtraction facts within 20

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Subtraction - Whole Number - Within 20

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Recall subtraction facts within 20

Detailed Explanation: Recall subtraction facts within 20

Learn by doing: Recall subtraction facts within 20

Practice with unlimited practice problems

Practice:

Subtraction - Whole Number - Within 20