Doubling and near-doubling
Maths · Key Stage 1 · The School
What doubling means
Double a number means add it to itself. Double 6 is 6 + 6 = 12. Double 10 is 10 + 10 = 20. Learn the doubles from double 1 to double 10 by heart. Then a whole set of sums becomes instant.
Near-doubling: one away from a double
6 + 7 is not a double. But it sits right next to one. It is double 6, plus 1 more. Double 6 is 12. So 6 + 7 = 13. Spot two numbers that are almost the same. Use the double you know. Adjust by 1.
Checking a near-double two ways
8 + 9 sits next to double 8. It also sits next to double 9. From double 8: 16 + 1 = 17. From double 9: 18 − 1 = 17. Both give 17. Two routes, one answer. That agreement is the check.
A near-double, worked step by step
4 + 5. Is this near a double? Yes. 4 is one less than 5. Use double 5. Take one away. Double 5 is 10. So 4 + 5 = 10 − 1 = 9. Or use double 4. Add one. Double 4 is 8. So 4 + 5 = 8 + 1 = 9.
Why doubles are worth learning
Doubles come back again and again. They help with near-doubling. They give you the 2 times table for free. Later they help with halving too, since halving is doubling in reverse. Ten facts, learned once, make years of sums faster.