You’re trying to attend a secret meeting, but the doorman just keeps saying numbers at you! You notice that other people seem to know what number to reply with, so there must be a pattern.

In this activity, detectives must use what they know about math operations to find patterns. Once they crack the doorman’s code, see what codes they can come up with by themselves!

This is an adaptation of the activity used by Zoom, created by WGBH in Boston, Massachusetts.