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A witch claims that she can predict whether your baby will be a boy or girl, and she charges £100 for this service.
If her prediction is wrong, she offers to return your £100 fee and pay you an extra £50 compensation for any distress that she may have caused.
Assuming she does not have any supernatural powers, can you explain whether she is likely to make a profit or loss after 100 clients have given birth?
If you liked this problem, you might also like the article it appears in, Con Tricks
Boy or Girl?
Age 14 to 16
ShortChallenge Level 
A witch claims that she can predict whether your baby will be a boy or girl, and she charges £100 for this service.
If her prediction is wrong, she offers to return your £100 fee and pay you an extra £50 compensation for any distress that she may have caused.
Assuming she does not have any supernatural powers, can you explain whether she is likely to make a profit or loss after 100 clients have given birth?
If you liked this problem, you might also like the article it appears in, Con Tricks
You can find more short problems, arranged by curriculum topic, in our short problems collection.
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