In the previous lesson Factor It, students found they could identify all the factors of a number without writing a large, cumbersome list. In this warm up, students play red light, green light to decide when they have identified all the factors.

Place students in pairs. Students will take turns factoring with their partner. Student A will be assigned a number to factor, Student B will act as the traffic monitor. As Student A begins factoring, Student B will pay close attention. After writing each factor pair, Student B will announce "red light" (meaning to stop) or "green light" (meaning to continue).

If Student A misses a factor (runs a light), Student B will give them a ticket. If Student B announces the wrong light color, Student A will give them a complaint. When one number is factored, students will swap places. The student with the fewest slips (both tickets and complaints) will win.

This warm up allows students to continue to practice factoring while keeping in mind the markers to look for to know when factoring is complete.