Sidewalk activities can make math fun for everyone. Try these:

Puddle watch. Have your child use washable chalk to trace around a puddle after rain. Every hour, have him chart how much the puddle has changed. Have him compare the rate of change in two puddles—one in the shade, the other in the sun.

Cut it up. Pick a segment of the sidewalk. Have your child draw lines to divide it into as many pieces as possible. Have him name all the shapes he has made: square, rectangle, etc.

Add it up. Help your child draw a 3-foot-by-3-foot grid on the sidewalk. Fill in each square with a different number, from 1 to 9. Take turns tossing two stones on the grid. Add up the two numbers on which the stones fall, and write this down. Do this for five rounds. Add up the five scores to see who got the highest score.

Mark your shadows. Have your child stand in the sunlight and make shadows on the sidewalk. Trace where his feet are. Draw a line at the end of his shadow and write the time of day. Do this every half-hour, standing in the same spot. Measure the shadows’ changes.