Acorn Mystery Picture: To 20, crossing ten

An acorn with a textured brown cap, a short stem and a smooth orange nut ending in a little point. The cap shows up first, so children can guess the picture before they finish.

All addition and subtraction facts up to 20 are mixed, including the ones that bridge ten. A child meets 9 + 4, 7 + 6 and 8 + 8 alongside 15 − 7, 12 − 9 and 11 − 3, plus easier problems that stay within one ten. Fluency here usually comes from make-ten strategies (9 + 4 = 9 + 1 + 3) or from doubles and near doubles (7 + 8 is one more than 7 + 7). Having both kinds on one page trains children to spot which strategy each problem calls for.