This issue's puzzle is from Mindbenders and brainteasers by David Wells and Rob Eastaway, reviewed in this issue of Plus.

Rolling with money

Sue was fiddling wth two 10p coins, rolling one of them round the other. Martin came over. "You see these two identical coins?" said Sue. "I am going to keep the one on the right still while I roll the one on the left round it without it slipping or sliding. What do you think will happen to the Queen's head when it gets to the other side?"

"The head will be upside down, of course!" Martin replied. Sue smiled smugly.

What is the correct answer?

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If you are stumped by last issue's puzzle, here is the solution.

For some challenging mathematical puzzles, see the NRICH puzzles from this month or last month.