Mountains Mystery Picture: Adding & subtracting to 30

Two grey mountains with snowy peaks, green hills in front and a yellow sun in the sky. The peaks appear first and the slopes grow wider row by row, so the landscape takes shape quickly.

Children add and subtract with numbers up to 30 and cross ten along the way: 17 + 6, 26 − 8, 19 + 5, 30 − 12. Since every answer has to match a row on the grid, results never go past the height of the picture, and the bigger numbers appear mostly as the starting number in a subtraction, such as 27 − 9 or 24 − 7. That makes this topic particularly strong on subtracting across a ten from the twenties, which many children find harder than adding.