How to explain doubles facts to a child
"Doubles" means you have two of the same number. For example, 4 + 4 is a doubles fact because both numbers are 4. If you know that 4 + 4 = 8, you can use that to help with other problems, like 4 + 5 or 8 − 4. Doubles facts are like little math shortcuts!
Worked examples with doubles facts
Example 1 (younger learners): Using a doubles fact within 20
Problem: 6 + 6 = ?
Think of 6 + 6 as a doubles fact, because the same number is added to itself. You can picture 6 toy cars and then 6 more toy cars. Put them together: 6 + 6 = 12. So the doubles fact is 6 + 6 = 12.
Example 2 (older learners): Using a doubles fact to solve a near doubles problem
Problem: 7 + 8 = ?
First, use the doubles fact you know: 7 + 7 = 14. The problem 7 + 8 is just 1 more than 7 + 7, because 8 is 1 more than 7. So add 1 to 14: 14 + 1 = 15. Using the doubles fact 7 + 7 = 14 helps you solve 7 + 8 = 15 quickly.
Going deeper with doubles facts
Doubles facts within 20, such as 1 + 1 up through 10 + 10, give your child a set of sums they can remember and use to solve other problems. When a child knows these facts automatically, it becomes easier to add within 20 using strategies instead of counting one by one.
One common strategy is "near doubles," where a problem like 8 + 9 is solved by starting with the doubles fact 8 + 8 = 16, then adding 1 more to get 17. This connects directly to addition within 20 and helps your child move from counting strategies to more efficient mental math.
Doubles facts also support subtraction. For example, if a child knows 6 + 6 = 12, then 12 − 6 must be 6. Later, the idea of doubling shows up in early multiplication, such as using "double and double again" to find 2 × 4 (double 4 to get 8) or 4 × 4 (double 4 to get 8, then double 8 to get 16).
Common mistakes with doubles facts
- Mixing up a doubles fact with a near doubles fact. A child might treat 5 + 6 as if it were the doubles fact 5 + 5 and say 5 + 6 = 10. Correction: Remind them that 5 + 6 is 1 more than 5 + 5, so 5 + 6 = 11.
- Counting incorrectly when using doubles plus one. For 7 + 8, a child might know 7 + 7 = 14 but then count 14, 15, 16 and say the answer is 16. Correction: Emphasize that 8 is just 1 more than 7, so they only add 1 to 14, giving 15.
- Forgetting to connect doubles to subtraction. A child might know 4 + 4 = 8 but still guess at 8 − 4 and say 5. Correction: Show that if 4 + 4 makes 8, then taking 4 away from 8 must leave 4.
Where doubles facts show up in everyday life
Doubles facts appear whenever there are two equal groups. If there are 5 apples in one bag and 5 apples in another, that is the doubles fact 5 + 5 = 10. Two matching rows of game pieces, 3 stickers on each of two pages, or 7 points scored in each of two rounds are all real-life doubles situations.