Addition within 20

Addition within 20 with the strategies that crack every fact, from make 10 to near doubles, plus practice.

🧒 Kids: add up to 20!

Use a trick for each fact. Tap Practice!

▶ Practice ⏱️ 1-minute challenge 🎮 Addition games

The 9 + facts: add 10, take 1

  1. 9 + 2 = 11
  2. 9 + 3 = 12
  3. 9 + 4 = 13
  4. 9 + 5 = 14
  5. 9 + 6 = 15
  6. 9 + 7 = 16
  7. 9 + 8 = 17
  8. 9 + 9 = 18

💡 Trick: 9 + 6? 10 + 6 = 16, take 1: 15!

More facts: Within 5 · Counting on · Within 10 · Make 10 · Doubles · Within 20

For parents and teachers ↓

This part is for grown-ups: the trick that makes these facts easy, pictures to draw, what to say, common mistakes, questions with answers and a free worksheet.

The trick: pick the right strategy

Within 20 there are too many facts to count on every time, so children choose a strategy. Small numbers: count on. Same or next-door numbers: doubles and near doubles. Crossing 10: make 10. Adding 9: add 10 and take 1. By the end of grade 2 most answers become memory.

Patterns to spot

See it: pictures to draw with your child

Draw these on paper or a whiteboard. Seeing the counters makes the fact stick.

9 + 6: move 1 counter to fill the first frame. 10 + 5 = 15.
567891011121314151617181920+3+5
7 + 8 on a number line: hop 3 to reach 10, then 5 more. 7 + 8 = 15.

Facts you already know

If your child knows the facts within 10, the pairs that make 10 and the doubles, they already have most of the facts to 20. The ones left are the teen facts that cross 10, like 8 + 5, 9 + 7 and 7 + 6, and every one of those can be done with make 10 or a near double.

In real life: Look for chances to add past 10: two dice in a board game, the cost of two small things, the number of children at a party. Ask “is it more than 10 or less?” before working it out.

Worked examples

Example 1: 8 + 5 with make 10

  1. 8 needs 2 to make 10.
  2. Split 5 into 2 and 3.
  3. 8 + 2 = 10, then 10 + 3 = 13.
  4. So 8 + 5 = 13.

Example 2: 9 + 7 with add 10, take 1

  1. 9 is one less than 10.
  2. 10 + 7 = 17, then take away 1: 16.
  3. So 9 + 7 = 16.

Example 3: 12 + 5 with tens and ones

  1. 12 is 1 ten and 2 ones.
  2. Add the 5 ones: 2 + 5 = 7 ones.
  3. 1 ten and 7 ones is 17.
  4. So 12 + 5 = 17.

Common mistakes

Counting on large numbersCounts on 8 from 7, often off by one.Fix: use a near double or make 10 instead: 7 + 8 = 7 + 7 + 1.
Writing teen numbers backwardsWrites 15 as 51.Fix: say it as “ten and five”: the 1 ten comes first, then the 5 ones.
Using the wrong strategyTries make 10 on 6 + 2.Fix: small numbers are quicker to count on: 6… 7, 8.

What to say to your child

A short script for your first session. Pause after each line and let your child answer.

  1. “What is 9 + 6? Let’s make it easier. What is 10 + 6?” (16.)
  2. “9 is one less than 10. So 9 + 6 is…?” (15!)
  3. “Now 7 + 8. Which double is close?” (7 + 7 = 14.)
  4. “And 8 is one more than 7, so…?” (15.)
  5. “Look at the numbers first, then pick a trick.”

Questions to try (answers below)

Ask these out loud or write them down. The last one is a stretch.

  1. 10 + 7
  2. 9 + 5
  3. 8 + 7
  4. 6 + 7
  5. 8 + 5
  6. 4 + 9
  7. 7 + ? = 16
  8. Mia has 9 marbles and Leo has 8. How many marbles altogether?
  9. Stretch: 7 + 6 + 3 (look for a 10)
Show the answers
  1. 17
  2. 14
  3. 15
  4. 13
  5. 13
  6. 13
  7. 9
  8. 17
  9. 16

Games to play at home

Two-dice race

Roll two dice and add. First to call the total keeps the dice.

Bus stop

Count children getting on a bus: “12 are on. 5 more get on. How many now?”

Fact sort

Write facts on cards and sort them into piles: count on, doubles, make 10.

A 5-day plan for addition within 20

Ten minutes a day is enough. Short, regular practice helps facts stick far better than one long session.

Next week, repeat the round in the practice tool and compare the fact map. When most facts are green, move on to the next page.

By grade

Grade 1 (1.OA.C.6) adds within 20 using strategies and is fluent within 10. Grade 2 (2.OA.B.2) is fluent within 20 and knows all sums of two one-digit numbers from memory. In India this is class 1 and 2 maths.

More for each grade: Grade 1 math and the CBSE class 1 maths guide; Grade 2 math and the CBSE class 2 maths guide.

What comes next

Addition within 20 is the base for 2-digit addition in grade 2, where the same strategies grow: 38 + 7 uses make 10 (38 + 2 + 5 = 45), and 25 + 25 is a double. When the facts are quick, move on to 2-digit addition and the addition speed test.

Worksheet and more practice

Print a free worksheet with an answer key, or keep practicing online with the addition practice trainer.

← DoublesAll addition practice →

More: addition for kids · addition facts strategies · addition chart · number bonds

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Questions parents ask

What is addition within 20?

Adding numbers with a total of 20 or less, such as 8 + 7 or 12 + 5. These facts are learned in grades 1 and 2.

How do kids learn addition facts within 20?

With strategies: count on for small numbers, doubles and near doubles, make 10, and add 10 take 1 for facts with 9.

What are the hardest addition facts within 20?

The facts that cross 10, like 8 + 5, 7 + 6 and 9 + 8. Make 10 and near doubles make each of these easy to work out.

When should kids know addition within 20 by heart?

By the end of grade 2. Common Core 2.OA.B.2 asks children to know all sums of two one-digit numbers from memory.

How can I practice addition within 20 at home?

Dice games, a quick fact a day in the car, and the online practice on this page. Short, daily practice works best.