Rob Eastaway solving a tricky problem
Media playback is unsupported on your device
Video

#BBCtrending: Here's the solution to that difficult maths problem

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

For more videos subscribe to BBC Trending's YouTube channel.

You can follow BBC Trending on Twitter @BBCtrending. All our stories are at bbc.com/trending

  • 05 Jun 2015
Go to next video: Is it wrong to call someone 'plus-size'?