The first European girls-only "mathematical Olympiad" competition is being hosted by Cambridge University.
The event is designed to encourage more girls to study and compete in maths.
It comes just days after researchers at the university revealed many higher education institutions felt A-levels did not stretch pupils enough.
Olympiad co-director, Dr Ceri Fiddes, said competition questions encouraged "clever thinking rather than regurgitating a taught syllabus".
The girls-only event at Murray Edwards College (formerly New Hall) was set up after male participants outnumbered females by 11 to one at last year's international Olympiad in Amsterdam.
Nineteen teams from across Europe are taking part in the new competition, organised in conjunction with education charity, the United Kingdom Mathematics Trust (UKMT).
The four-girl teams are expected to solve eight "very difficult problems" during nine hours of examinations.
"A lot of Olympiad questions in the competition are about proving things," Dr Fiddes said.
"If you have a puzzle, it's not good enough to give one answer. You have to prove that it's the only possible answer.
"It's not at all like A-level maths where you get taught a certain syllabus, and when you sit the exams you have to regurgitate what you've been taught, and perhaps use it a little bit.
"In the Olympiad it's about starting with a problem that anybody could understand, then coming up with that clever idea that enables you to solve it," she said.
"For example, take the numbers one up to 17.
"Can you write them out in a line so that every pair of numbers that are next to each other, adds up to give a square number?
"You might be able to play around with that and stumble across an answer, but that's not good enough.
"You can't just say 'here's an answer'. You have to find all possible answers and prove you had found them all.
"Having this skill of problem-solving and logical thinking is really useful, especially in writing computer programmes," she added.
'Focus for excellence'
Taking part in this year's competition, which ends on Monday, is 17-year-old Natalie Behague, from Kent.
A member of the UK team, she said she had been interested in maths since the age of 13 and hoped to gain a place at Cambridge University.
"It's challenging. You have to think and stretch your mind a bit," she said.
"I just enjoy doing maths, so perhaps becoming an academic in the field of mathematics would be good."
Television presenter and mathematician Carol Vorderman is a keen advocate of the Olympiad.
She said: "It's always great to have a focus for excellence, and this will help bring on many female maths stars of the future.
"These children are critical for our economic success in the years to come. They will drive the industries of the future."