Adding by making ten
Maths · Key Stage 1 · The School
Ten is the magnet
Adding is easiest through 10. The bonds that make 10 — 1+9, 2+8, 3+7, 4+6, 5+5 — should be as fast as your own name. They are the tools for everything bigger.
Bridging through ten
For 8 + 5, do not count on your fingers five times. Steal from the 5 just enough to make 10: 8 needs 2, so take 2 from the 5 (leaving 3). Now it is 10 + 3 = 13. One split, one easy add.
Say the bridge
Saying it fixes it: "8 and 2 makes 10, and 3 more makes 13." Try 7 + 6: "7 and 3 makes 10, and 3 more makes 13." The out-loud pattern becomes the in-head pattern.
Put the bigger number first
For 3 + 9 you could bridge from the 3, but there is an easier way: swap them. 3 + 9 is the same as 9 + 3, because adding does not care which number comes first. Now bridge: 9 and 1 makes 10, and 2 more makes 12. Swapping turns a hard bridge into an easy one, and you are allowed to do it every single time you add. One warning: this works for adding only. Taking away does care about order — 9 take away 3 is 6, but 3 take away 9 is not 6 at all.