What is this skill?
Adding within 10 covers all the sums up to ten, such as 6 + 3, 4 + 4 or 2 + 7. Children are expected to solve these with objects, drawings, fingers or mental strategies and to write the matching equation. It extends adding within 5 to bigger numbers, where counting everything from one starts to become slow.
The key strategy at this level is counting on: start with the bigger number and count up the smaller one. For 2 + 7, start at 7 and count "eight, nine" to get 9. Children also notice that order does not change a sum: 2 + 7 and 7 + 2 are both 9, which means fewer facts to remember.
Why it matters
Sums within 10 are the core addition facts that everything else rests on. First graders use them to add within 20, second graders to add two-digit numbers, and third graders to multiply. A child who still needs to count on fingers for 6 + 3 in second grade will find multi-step problems much harder, so building fluency with these facts over time is worthwhile.
Fluency should grow from understanding, though, not from rote drilling. Children who know why 4 + 4 = 8 and can picture it are far better at recalling it than children who memorized it as a sound.
Common mistakes
- Counting the starting number twice when counting on: for 6 + 3, saying "six, seven, eight" and answering 8. The fix is to say the first number, then count the next three: "six... seven, eight, nine."
- Always starting from the first number even when it is small, so 2 + 7 means counting on 7. Encourage your child to start with the bigger number.
- Losing count on fingers when both numbers are big. Using a ten frame or two groups of objects helps children see the whole sum.
How to help at home
- Roll two dice and add the dots. Dice are a great tool because children quickly start recognizing dot patterns instead of counting every dot.
- Practice doubles, which children often learn quickly: 1 + 1, 2 + 2, up to 5 + 5. Then use them for near-doubles: if 4 + 4 = 8, what is 4 + 5?
- When your child counts on, ask them to say the first number out loud and then put up a finger for each number they count after it.
- Ask your child to make up addition stories for you to solve. Writing problems is often harder, and more revealing, than solving them. Get one wrong on purpose now and then and let your child correct you. Spotting your mistake takes real understanding.
Worked examples
These are real questions from the Tutorsaurus adding to 10 practice, with the answers worked out.
Example 1
7 + 3 = ?
Choices: 10, 7, 8, 11
Answer: 10. 7 + 3 = 10. Start at 7 and count on 3.
Example 2
5 + 4 = ?
Choices: 8, 7, 9, 6
Answer: 9. 5 + 4 = 9. Start at 5 and count on 4.
Example 3
8 + 2 = ?
Choices: 10, 8, 11, 12
Answer: 10. 8 + 2 = 10. Start at 8 and count on 2.