Teenagers from around the world are pitting their wits against some of the toughest maths questions around in a competition at Strathclyde University.

Children of secondary school age from 85 countries are taking part in what is billed as the Olympics of the maths world - the 43rd International Mathematical Olympiad (IMO).

A total of 500 students have come from as far afield as Kazakhstan and South Korea.

Six children from the UK are taking part - five boys and a girl, who are all aged between 15 and 18.

They were chosen out of 40,000 secondary school pupils.

'Tough problems'

The contestants will sit two exams - on Wednesday and Thursday - which will last a total of nine hours.

There are three questions in each test.

Strathclyde university's professor of maths, Adam McBride, says the questions are very difficult.

"I honestly would not be able to answer them - they are really, really tough problems.

"You require a young mind and mine is far too old for this kind of thing nowadays."

The youngest person taking part is a 14-year-old girl from Puerto Rico.

The competition ends on 30 July, when the Princess Royal will present prizes to the winners.

The competition was last held in Britain in 1979, when it was staged in Oxford.