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Doorman's Code graphic

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.

Math Mess: The Bulging Briefcase
Cookie Monster's Investigation

Related Lessons

  • Lesson 13

    Divide two- and three-digit numbers by a single-digit number using strategies based on place value (partial quotients). Divide multi-digit numbers by a single-digit number using strategies based on place value.

  • Lesson 14

    Use estimation and visual models to solve problems involving adding fractions with unlike denominators. Use visual models to solve problems involving adding fractions with unlike denominators.

  • Lesson 15

    Use visual models to solve problems with division to divide unit fractions by whole numbers and whole numbers by unit fractions. Use visual models to solve problems with division of unit fractions & whole numbers.