Image caption Students have petitioned Sheffield University to investigate the exam paper

Final year economics students at Sheffield University are furious after an exam this week contained questions they found "impossible".

The paper, on the economics of cities, contained compulsory questions on topics they had never been taught, say the students.

More than 90% of those who took the exam have now signed an online petition demanding the university investigate.

The university said all questions were based on topics taught in the course.

But, in a tweet, one candidate complained: "Question three may as well have been in Chinese."

Another asked: "How can they write a paper and include questions on something we haven't been taught, or told to research?"

Just over 100 students took the exam on Wednesday.

Degree fears

Almost all of these have nowalien to us. We had never seen it before and had never seen the terms it used," said one.

Another said it was "completely unfair... impossible to do".

This meant there was no choice, students had to answer the other two questions. Even this was not straightforward as one of the remaining questions asked candidates to compare two economic studies, one of which had not been part of their course.

On Twitter, students called it an "absolute disgrace", "an exam from hell", "unethical", "poorly set and horrible beyond words after sleepless nights".

Adjustments 'considered'

As well as students taking a BSc in economics, the paper was sat by students taking a joint BA honours with other subjects, such as politics.

The joint honours students were particularly badly affected as many lacked the mathematical background