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In this number puzzle/trick, learner #1 thinks of a number between 1 and 63. Learner #2 shows learner #1 six cards and asks them whether the cards contain their number. Learner #2 uses this information and the cards to determine the number in learner #1's head. This guide also contains an animation in which the computer attempts to guess your number. Use this activity to explain binary arithmetic.

Quick Guide

Preparation Time:
Under 5 minutes

Learning Time:
5 to 10 minutes

Estimated Materials Cost:
1 cent - $1 per group of students

Age Range:
Ages 14 - 18

Resource Types:
Activity, Game


Materials List (per group of students)


  • Mathematics
    • Number and Operations
      • Number Systems
    • Reasoning and Proof
  • The Nature of Technology
    • The Design Process
      • Problem Solving

Informal Categories

  • Games


To use this activity, learners need to:

  • see
  • read
  • touch

Learning styles supported:

  • Involves hands-on or lab activities


Components that are part of this resource:

Access Rights:

  • Free access



  • All rights reserved, University of Cambridge, 2007