Print out the following pages and laminate them. Cut apart.
Place one island on each desk in order 1-20. Have students start at a number and circle it on their answer sheet. Set your timer for 1 minute. Students will have 1 minute to do each perimeter problem. Then they will rotate to the next number. Once they get to number 20, they will rotate to the beginning and start on number 1. After everyone has completed each problem, check their answers for a reward!
This can also be used in a center for extra practice or with small groups.