Skip to content# Simplex Locks

**Classifications**

Author(s): Amy Myers

A simplex lock is a type of combination door lock that involves pushing-in buttons. Given the set of rules for using a 5-button simplex lock, how many different combinations are there?

Topics covered: Combinatorics

Mathematical practices: MP7 – Look for and make use of structure., MP8 – Look for and express regularity in repeated reasoning.

Supporting materials: Facilitator Guides

Associated Math Circles: MTC Network, Philadelphia Area Math Teachersâ€™ Circle