Mystery Jars: Make Your Own: Estimating and Counting

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Learners make a counting/estimating jar to exchange with friends or bring home. Each learner fills a clear plastic cup with small objects such as beads or pennies and keeps count of exactly how many are in the cup. Others have to estimate how many are in the cup. Younger learners use larger objects, so only up to about 15 fill the cup; older ones can use smaller objects, so 50 or more fill the cup. [Activity is publicly available through a web crawler capture on]

Quick Guide

Preparation Time:
Under 5 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:
1 cent - $1 per student

Age Range:
Ages 4 - 14

Resource Types:
Activity, Game


Materials List (per student)

  • clear plastic cups, about 8 oz
  • rubber bands
  • plastic wrap
  • objects for filling cups, such as beads, pasta, pompoms
  • scrap paper and pencils


  • Mathematics
    • Geometry
      • Solid Geometry
    • Measurement
      • Units of Measurement
      • Size and Scale
    • Number and Operations
      • Multiples and Factors
      • Number Systems
      • Operations
    • Reasoning and Proof
  • The Nature of Technology
    • The Design Process
      • Problem Solving
  • The Nature of Science
    • The Scientific Process
      • Asking Questions
      • Formulating Explanations
      • Communicating Results

Informal Categories

  • Arts and Crafts
  • Games


To use this activity, learners need to:

  • see

Learning styles supported:

  • Involves hands-on or lab activities


Access Rights:

  • Free access


Source Collection

  • Mixing in Math


  • , © 2010, TERC, Inc., MA., 2010

Funding Source:

  • NSF, ESI-0406675 and DRL-0713537