Category: Puzzle

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Brothers

Here’s an old puzzle, but a good one. Try to answer before you look at the next page. Also, assume the likelihood of a boy or girl is the same (it just makes it easier).

Mr and Mrs Jones have two children. One is a boy.

What is the probability the other is a boy?

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Puzzle

A family member sent me a puzzle the other day. It had apparently appeared on tv in a quiz and was worth close to £100,000.

I did not see the show, and here is my version of the question:

there are 100 people in a room. 99% are left handed. How many left handed people need to leave the room to bring the percentage down to 98%?

There are plenty of people doing this on-line, including this:

It’s fine to do it by algebra, but you couldn’t and wouldn’t use this method on tv in a timed quiz for a huge sum of money. But we know why he has posted this – the arithmetic is really interesting.

Have a go yourself, then look at the next page.

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