Complements of 10
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Complements of 10: skill guide
| Objective | A complement of 10 is the amount needed to join another amount and make 10. |
|---|---|
| Grade | Kindergarten |
| Standard | CCSS.MATH.CONTENT.K.OA.A.4 |
| Difficulty | Foundational · Abstract |
| Representation | Numerals |
| Practice format | Interactive, account-free practice with immediate feedback |
Objective
A complement of 10 is the amount needed to join another amount and make 10.
What this practice covers
A complement of 10 is the amount needed to join another amount and make 10. Every problem fills a complete ten frame with two colors. Red dots show the known part, while green dots show its complement. Because the frame is arranged as two rows of five, learners can use the structure of five and ten instead of counting every dot. The paired colors connect a visual model with equations such as 6 + 4 = 10 and 4 + 6 = 10.
Standards alignment
Supports Common Core: CCSS.MATH.CONTENT.K.OA.A.4 — For any number from 1 to 9, find the number that makes 10.
Who it’s for
This practice is designed for kindergarten learners who recognize quantities through ten and are beginning to learn number bonds. It is also useful for learners who can calculate sums but need a clearer visual understanding of why two numbers combine to make ten.
What to know first
- Learners should count reliably to ten and recognize a full ten frame. Familiarity with addition as joining two parts is helpful. Automatic recall is not expected: the frame is present so learners can reason from what they see.
Difficulty and scaffolding
Foundational · Abstract stage
Problem representations
- Numerals
Three worked examples
- If 7 dots are red, the remaining 3 are green. The two parts make the full frame: 7 + 3 = 10.
- If 5 dots are red, 5 dots are green. Two full rows of five show the doubles fact 5 + 5 = 10.
- If all 10 dots are red, no green dots are needed. This shows 10 + 0 = 10.
Likely misconceptions
- Learners may report the red amount instead of the green complement, count a cell rather than its dot, or stop after the first row. Read the color named in the question before answering. Then use the full frame as evidence: the two colored groups must always total ten. When one part is larger, the other must be smaller.
Hints and explanations
- If 7 dots are red, the remaining 3 are green. The two parts make the full frame: 7 + 3 = 10.
- If 5 dots are red, 5 dots are green. Two full rows of five show the doubles fact 5 + 5 = 10.
- If all 10 dots are red, no green dots are needed. This shows 10 + 0 = 10.
What to practice next
Practice recalling the same number bonds without a picture, then reverse them as missing-addend equations such as 8 + ? = 10. The next ten-strip practice presents the same complements in one row, strengthening the connection between groups, length, and equations.
Editorial review
Reviewed by Brilliant’s curriculum team. Exercises are generated within defined difficulty ranges and checked against verified answer rules.
Complements of 10 FAQs
What is a complement of 10?
A complement of 10 is the number that combines with another number to make 10. For example, 3 and 7 are complements because 3 + 7 = 10. The relationship works in either order, so 7 + 3 also equals 10.
Why use two colors in the ten frame?
Two colors keep both parts visible while preserving one complete group of ten. A learner can see the known amount, the amount that completes it, and the whole at the same time. This supports number bonds more clearly than showing one group and several empty spaces.
Should learners memorize complements of 10?
Fluent recall is valuable, but understanding should come first. Let learners use the frame, explain the two parts, and notice patterns such as one part increasing while the other decreases. With repeated, accurate practice, the pairs usually become automatic without pressure.
How many problems should a learner practice at once?
A focused set of about 10–15 problems is usually enough for useful practice without fatigue. Stop earlier if attention or accuracy drops. Several calm sessions spread across a week are more effective than one long session. This activity offers a five-question quick check and a fifteen-question practice with immediate feedback after every answer.
How do complements of 10 help with addition?
Making ten is a powerful mental-math strategy. To solve 8 + 5, a learner can split 5 into 2 and 3, use 8 + 2 to make 10, and then add the remaining 3. Knowing complements makes that rearrangement much easier.