Nowadays governments have their hands so deep in your pocket that the first recourse in tackling any problem – especially one caused by the politicians themselves – is to tax the citizen.

In Arbitraria they have just built 7 unnecessary bridges and have instituted a bridge tax to pay for them, which means that on crossing any bridge you must hand over half the number of pence you have on you plus half a penny. If you are carrying eggs you must hand over half the eggs plus half an egg.

One morning d’Artagnan set off with enough money to return home with a dozen eggs, which is the required number for any decent omelette. He had to cross 7 bridges to get to the Zoological Gardens where he bought eggs at a penny each from his brother-in-law. At each of the 7 bridges on the way home he duly handed over half his eggs plus half an egg. He arrived back home with the 12 eggs and made his omelette.

How much had his omelette cost?

Find the solution here.

Each issue, we award a prize to three lucky winners – this time we have copies of Brian Greene's The Hidden Reality, which is reviewed by Marcus Chown in this issue. You can send in your answers (complete with your postal address, if you want to win) to editor[at]newhumanist.org.uk. Deadline is 1 April 2011. We will publish the solution here shortly after that date.