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Sibling survey

By David, 15 May 2019 Brainteaser

Emily has twice as many brothers as she has sisters. Her brother Bill has one more sister than he has brothers. How many boys and girls are in Emily and Bill’s family?

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Brainteaser answer

This puzzle might seem impossible because Emily has more brothers than sisters, and Bill has more sisters than brothers. But both can be true if there are the same number of boys and girls in the family.

If there’s the same number of boys and girls, Emily must have one more brother than sister. The only way for her to have twice as many brothers than sisters is if she has one sister and two brothers.

Adding in Emily, there are two girls and two boys in the family.

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3 comments

  1. WOW!!!

      Reply
  2. b = boys; g= girls
    per Emily b = 2g -1
    per Bill b +1 = g

    solve

      Reply
  3. Not quite: b=2(g-1) and b=g

      Reply

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