Number pairs that make 20
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Number pairs that make 20: skill guide
| Objective | Learners use 20 dots in ten strips to find how many more make 20, starting from a number between 10 and 19. |
|---|---|
| Grade | Grade 1 |
| Standard | CCSS.MATH.CONTENT.1.OA.C.6 |
| Difficulty | Developing · Mixed |
| Representation | Ten strip, Numerals |
| Practice format | Interactive, account-free practice with immediate feedback |
Objective
Learners use 20 dots in ten strips to find how many more make 20, starting from a number between 10 and 19.
What this practice covers
Each problem shows 20 dots in two ten strips and an equation such as 14 + □ = 20. The blue dots match the first number, which is from 10 to 19, and the orange dots fill the rest of the strips. The learner chooses how many more dots make 20 from the numbers 0 to 10. Counting the orange dots or counting on from the first number both give the answer.
Standards alignment
Supports Common Core: CCSS.MATH.CONTENT.1.OA.C.6 — Add and subtract within 20 using strategies such as making ten.
Who it’s for
This practice is designed for Grade 1 learners building fluency with addition within 20. It is also useful for older learners who want a quick visual review of the number pairs that make 20.
What to know first
- Learners should count reliably to 20, read two-digit numerals, and understand addition as joining parts.
Difficulty and scaffolding
Developing · Mixed stage
Problem representations
- Ten strip
- Numerals
Three worked examples
- 14 + □ = 20: the strips show 14 blue dots and 6 orange dots, so 14 + 6 = 20.
- 17 + □ = 20: count on from 17 to 18, 19, 20. That is 3 more, so 17 + 3 = 20.
- 10 + □ = 20: the first strip is all blue and the second strip is all orange, so 10 + 10 = 20.
Likely misconceptions
- Learners may count all 20 dots instead of only the orange ones, or choose the ones digit of the first number, as in 4 for 14 + □ = 20. Point to the full strip of ten first, then count the orange dots that complete the second strip.
Hints and explanations
- 14 + □ = 20: the strips show 14 blue dots and 6 orange dots, so 14 + 6 = 20.
- 17 + □ = 20: count on from 17 to 18, 19, 20. That is 3 more, so 17 + 3 = 20.
- 10 + □ = 20: the first strip is all blue and the second strip is all orange, so 10 + 10 = 20.
What to practice next
Next, solve the same make-20 equations with numerals only, without dots to count.
Editorial review
Reviewed by Brilliant’s curriculum team. Exercises are generated within defined difficulty ranges and checked against verified answer rules.
Number pairs that make 20 FAQs
What is the goal of number pairs that make 20?
The goal is to find the number that makes 20 with any number from 10 to 19. A learner should be able to say what the blue and orange dots stand for and find the answer without recounting every dot.
Should this practice be timed?
No timer is required. First build accurate, understandable strategies. Speed usually improves naturally as learners recognize groups of ten, familiar facts, and repeated patterns.
What should a learner do after a mistake?
Point to the orange dots and count them, then read the equation aloud with that number in the blank. A short explanation is more valuable than immediately repeating the same guess.
How many problems should be completed at once?
A Quick check has 5 problems and a Practice session has 15. A learner may pause when attention drops. A short, successful session with clear reasoning is more useful than rushing through a longer set.