Here's the solution to that 'impossible' maths problem

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Media captionRob Eastaway, author of "Maths for Mums and Dads", shows the solution.

When British mathematics students tumbled out of this year's GCSE exam (given to 16-year-olds), one question was on their minds.

A fiendishly difficult problem involving a girl named Hannah with two different colours of sweets stumped thousands - and many took to Twitter to complain. Nearly 200,000 people tweeted #edexcelmaths after the exam was finished on Thursday (Edexcel, owned by global publishing and education giant Pearson, is the company that administers the exam).

Radio 4's More or Less asked Rob Eastaway, author of "Maths for Mums and Dads", to show how the problem can be solved. If you'd like to have a go before watching the solution, here's the question in full:

There are n sweets in a bag.

6 of the sweets are orange.

The rest of the sweets are yellow.

Hannah takes at random a sweet from the bag.

She eats the sweet.

Hannah then takes at random another sweet from the bag.

She eats the sweet.

The probability that Hannah eats two orange sweets is 1/3

(a) Show that n^2 - n - 90 = 0

(b) Solve n^2 - n - 90 = 0 to find the value of n

Video journalist: Alvaro A. Ricciardelli

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