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How Many Balls?

Age 16 to 18
Challenge Level Yellow star
  • Problem
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Decide on the unknowns and assign letters to them. Take the information given step by stepand write down expressions for the probabilities. Can you obtain an equation and solve it?

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The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.

NRICH is part of the family of activities in the Millennium Mathematics Project.

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