Free interactive math game: Number Bonds to 10 — Pairs that make 10. Part of the Learning Numbers category on MathKite.
Taken from the generator that powers this exercise. A fresh set appears every time the page is opened, and the printable worksheet holds ten of them.
Knowing by heart which pairs of numbers add up to ten — the single most useful fact in mental arithmetic.
Count on from the number you are given until you reach ten, or recall the pair directly. The pairs are 1 and 9, 2 and 8, 3 and 7, 4 and 6, and 5 with itself.
For 3 + ? = 10, count up from three: 4, 5, 6, 7, 8, 9, 10. That is seven steps, so the answer is 7.
Answering with the number you started from. Reading the finished sentence back, 3 + 7 = 10, catches this immediately.