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Grade 2 · Maths · Lessons
Every fact to twenty
🤝partners🔟ten➕add➖take away
Number partners.
The big ideaOne fact gives four. Know them by heart.

How it works

Numbers come in families. If you know 7 + 8 = 15, you also know 8 + 7 = 15, 15 − 7 = 8 and 15 − 8 = 7.

Make a ten to help: 8 + 5 is 8 + 2 to reach ten, then 3 more.

The more you practise, the more facts you know by heart.

7 + 8 = 158 + 7 = 1515 − 7 = 815 − 8 = 7
One fact family: four facts from three numbers.

Example 1: A missing part

  1. 7 + ? = 15
  2. The whole and one part are given. Think of the partner that makes the whole.
  3. Use a fact you know, or make a ten.
  4. So the answer is 8.

Example 2: A take-away fact

  1. ? = 12 − 8
  2. Turn it round: what must I add to the small number to reach the big one?
  3. That missing number is the answer.
  4. So the answer is 4.

Example 3: A fact with a hidden answer

  1. 5 − 1 = ?
  2. Say the fact family out loud.
  3. One of its four facts has the answer in it.
  4. So the answer is 4.

Words to know

fact family
Facts that use the same three numbers.
partner
The number that goes with another to make a total.

Watch out

Try it

  1. 2 − 1 = ?
  2. ? = 15 − 8
  3. ? = 10 − 9
Answers: 1. 1 · 2. 7 · 3. 1
For grown-upsSay a number to 20 and ask for its partner to make 10, then to make 20. A few minutes in the car works well.
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