Construct simple self-checking math devices.

Cut pieces of cardboard 25 cm ( 10") long and 10 cm (4") wide.
Notch both edges at 1.25 cm (1/2") intervals.

Print 20 multiplication and division facts near the notches on one side; the answers, randomIy, on the other.

Working independently, children stretch rubber bands across the notches that connect the facts and answers.

The device becomes self-checking when you draw tines on the back of the cardboard connecting the appropriate notches.

If rubber bands cover all lines, the students know their answers are correct.