What is this skill?
Subtracting within 10 covers problems such as 9 − 4, 7 − 7 or 10 − 3. Children solve them by taking away objects, drawing and crossing out, counting back on a number line, or thinking about the matching addition fact. They also write the equation with the minus and equals signs.
Counting back is the subtraction partner of counting on. For 8 − 3, start at 8 and count back three: "seven, six, five." Another way to think is "3 plus what makes 8?" which turns a subtraction problem into an addition one.
Why it matters
These facts are the basis for subtracting within 20 in first grade and with bigger numbers after that. The link between addition and subtraction matters most: children who see that 8 − 3 = 5 because 5 + 3 = 8 have half as many facts to learn, and a way to check their work.
Subtraction also has more than one meaning: taking away, but also comparing ("how many more?") and finding a missing part. Meeting these meanings early makes word problems in later grades much less confusing.
Working within 10 keeps every problem small enough to act out with fingers or objects, so children can always check an answer for themselves. That independence matters: a child who can prove that 9 − 4 is 5 by counting back on their fingers does not need to guess, and is far less likely to feel anxious about subtraction later.
Common mistakes
- Starting the count back on the first number: for 8 − 3, saying "eight, seven, six" and answering 6. Remind your child that the first number is where you start, not the first step.
- Subtracting the smaller number from the larger even when the problem is written the other way round. At this level, problems always start with the bigger number; reading each problem aloud keeps the order straight.
- Not trusting a zero answer, as in 6 − 6. Act it out with objects so the answer "none left" makes sense.
How to help at home
- Play bowling with 10 empty plastic bottles. After each roll, ask how many fell and how many are still standing, and write it as a subtraction.
- Count back from 10 together, like a rocket launch, and then from other numbers. This builds the counting-back skill subtraction needs.
- When you solve a subtraction together, ask for the matching addition: "So 7 − 2 = 5. What is 5 + 2?"
- Use a number line on the floor made with tape. Your child stands on the first number and jumps back the second number of steps.
Worked examples
These are real questions from the Tutorsaurus subtracting within 10 practice, with the answers worked out.
Example 1
5 − 1 = ?
Choices: 3, 1, 4, 2
Answer: 4. 5 − 1 = 4. Count back 1 from 5.
Example 2
9 − 1 = ?
Choices: 6, 10, 8, 9
Answer: 8. 9 − 1 = 8. Count back 1 from 9.
Example 3
5 − 5 = ?
Choices: 0, 10, 3, 2
Answer: 0. 5 − 5 = 0. Count back 5 from 5.