Addition to 20 colour by code — rocket

Every problem here is constructed so the two numbers straddle ten (for example 8 + 5, not 8 + 1), because that is the specific case that trips children up after bonds-to-ten are secure. It is a narrower, harder skill than the within-10 sheet on purpose — the picture reward is the same size, the maths underneath it is not.

The self-checking mechanic matters more here than anywhere else in the set: crossing ten is exactly the kind of error a child makes silently and repeats, and a visibly wrong rocket catches it immediately instead of at the next test.