Addition and subtraction facts to 20: what children learn
This is a sprint game: children type as many answers as they can in 60 seconds. The questions include straightforward facts (9 + 6 = ?), subtractions (17 − 8 = ?) and missing number forms (? + 5 = 13). Regular short sprints are one of the best ways to build fluency, and the timer shows progress clearly.
Supports part of Common Core 2.OA.B.2. This focused game does not cover the entire standard.
Common Core connection: 2.OA.B.2. This is focused practice for part of the standard.
How to play
How many can you answer in 60 seconds? Type the answer and press Enter. Questions keep coming for 60 seconds. Type each answer and press Enter, or choose Skip. Answers can be typed with or without commas.
Step by step
- Know the bonds to 10. Most facts to 20 can be built from bonds to 10. If you know 7 + 3 = 10, then 7 + 4 is one more: 11.
- Use doubles and near doubles. Doubles such as 6 + 6 = 12 are easy to remember. Near doubles follow: 6 + 7 is double 6 plus 1, which is 13.
- Bridge through 10. For 9 + 6, take 1 from the 6 to make 10, leaving 5: 10 + 5 = 15. For 15 − 7, take 5 to reach 10, then 2 more: 8.
- Derive bigger facts. Once 3 + 7 = 10 is known, so is 30 + 70 = 100 and 100 − 70 = 30. This is what the curriculum means by 'derive and use related facts up to 100'.
Worked examples
Example 1: 9 + 6 = ?
Working: 9 + 1 = 10, and 5 more is 15.
Answer: 15
Example 2: 13 − 8 = ?
Working: Count up from 8: 2 more makes 10, then 3 more makes 13. 2 + 3 = 5.
Answer: 5
Example 3: ? + 7 = 16
Working: 16 − 7 = 9. Check: 9 + 7 = 16.
Answer: 9
Common mistakes and how to fix them
- Rushing and typing an answer that is one out. Being one out often comes from counting on or back. Practice the bridging strategy instead.
- Getting stuck on missing number questions. Turn them into subtraction: ? + 7 = 16 is the same as 16 − 7.
- Knowing facts one way round only. Practice fact families. If you know 8 + 5, you know 5 + 8, 13 − 5 and 13 − 8.
Activities to try at home
- Do one 60-second sprint a day and keep a chart of scores. Beat your best, not your sibling.
- Play 'make 20' with playing cards (picture cards removed): turn two over and work out the total, or how many more to reach 20.
- Ask quick facts while waiting in lines or walking to school.
Ideas for the classroom
- Display a 'strategy wall' with bonds to 10, doubles, near doubles and bridging, and ask students which strategy they used.
- Use the printable worksheet as a timed starter, then mark it with the answer sheet.
- Pair students to make up missing number questions for each other.
Free printable game and worksheet
The free printable starts with a game sheet, such as a color-by-answer picture, an answer maze or a secret-code joke, followed by a worksheet. Both use the same checked questions as the online game, and the answers are on the last page. Print it, or save it as a PDF from your browser’s print menu.
Open the free printable game and worksheet
Frequently asked questions
What does fluency with facts to 20 mean?
Being able to answer facts such as 8 + 7 or 15 − 9 quickly and accurately, usually in a few seconds, without counting in ones.
How does the sprint score work?
You get one point for each correct answer before the timer runs out. Wrong answers show the right answer and move on. Stars are awarded for 6, 12 and 18 correct.
Can I type answers on a phone?
Yes. The answer box opens a number keyboard on most phones and tablets.