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Brothers and Sisters

Age 11 to 14
ShortChallenge Level Yellow star
Secondary curriculum
  • Problem
  • Solutions


A boy has the same number of sisters as brothers.

Each of his sisters has only half as many sisters as brothers.

How many brothers and sisters are in the family altogether?




If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.


This problem is adapted from the World Mathematics Championships
You can find more short problems, arranged by curriculum topic, in our short problems collection.

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Albert Einstein could see two clocks which were out of sync. For what fraction of the day did they show the same time?

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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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