Toadstool Mystery Picture: Adding & subtracting to 100

A toadstool with a red cap full of white spots on a pale stem. The spots are the cells left uncolored, so the pattern appears by itself as the cap fills in.

Problems use two-digit numbers up to 100, mixing those with and without regrouping: 36 + 27, 45 + 30, 82 − 49, 70 − 26. Children practice adding tens and ones separately, trading ten ones for a ten, and subtracting when the ones digit on top is too small, as in 82 − 49. Mental strategies such as adding 30 and then 6 work well here, and so do column methods on scrap paper.