## Thursday, 14 July 2011

### Holiday puzzle solutions

For any readers who might be interested, here are the solutions to my holiday puzzles.

1) Merlin rode out from Camelot on Tuesday and returned five days later on Tuesday. How did he manage that?

Tuesday was the name of his horse!

Apologies to those of you who have been trying to do clever things with crossing the international date line at the speed of light, or locating Camelot on the North Pole.

2) What do you get if you subtract 17 from 374 twenty-two times?

I've done it 22 times and I got 357 each time.

3) A farmer owns a large square farm. Every Monday morning he walks around the four sides of his farm.

It takes him ninety minutes to walk along the first side. He then stops for a drink from the well.

It takes him ninety minutes to walk along the second side. He then stops for a rest under a tree.

It takes him ninety minutes to walk along the third side. He then stops to chat to the milkmaid.

He then walks along the fourth side, but this takes him an hour and a half!

Can you explain why?

Nothing to explain. 90 minutes is the same as an hour and a half. If you spotted this, well done. It might seem surprising, but there's something about the way this is worded that leads even very intelligent people into speculations about tiredness or what happened with the milkmaid.

4) Which has more tails? One kangaroo or no kangaroo?

Here's a nice play on words. "One kangaroo has one tail. No kangaroo has more than one tail. So, 'no kangaroo' has more tails than one kangaroo!"

5) What is the probability that the first person you see on leaving your house tomorrow will have more than the average number of legs?

It depends what is meant by 'average'.

If the 'average' is the mean number of legs, then the average number of legs would be just a tiny bit less than 2. So, it is almost certain that the first person I see on leaving my house will have more than the average number of legs. The probability is 'nearly 1'.

But if by 'average' we mean the modal number of legs (the most commonly occurring) or the median number of legs (the number of legs of the person in the middle if people are lined up in order of how many legs they have), then our average is two legs (precisely). The probability of seeing someone with more than two legs is just about zero!

6) If someone agrees to answer yes or no honestly to two questions, how can you then get them to agree to anything? For example, to say ‘yes’ to the question: ‘Will you give me a thousand pounds?’

Question 1: Will you answer the next question the same way as you answer this one?

Question 2: Will you give me a thousand pounds?