Exam question error in AS-level paper
Pupils taking an AS-level exam have been given a question that could not be answered - the second such problem this summer.
The latest unanswerable question was in a business studies paper set by the AQA exam board.
A teacher voiced fears that pupils had wasted so much time trying to answer the unanswerable question they had not had enough time for other questions.
The AQA exam board said it was "very sorry about the error in the paper".
"However, we do have a robust process for ensuring that none of our students will be disadvantaged as a result of our mistake," said a statement from the exam board.
The paper was taken by pupils in England, Wales and Northern Ireland.
A business teacher in Leicestershire contacted the BBC News website to complain about the difficulties faced by pupils who had taken the exam on 24 May.
The exam paper did not include the information needed to make the calculation to answer the question - which was about the profits of a chocolate company.
"Myself and my students are concerned as some recognised the error and left the answer blank and some spent far too long trying to figure it out and consequently ran out of time when doing the bigger mark questions towards the end of the exam," wrote the teacher, who did not want to be identified.
The AQA board has said: "The examiners who will be marking the paper are aware of the problem and marks will be adjusted to ensure that all students get the right grade."
The board said the question was worth three marks out of 80.
Last week it emerged students taking an AS-level maths paper set by the OCR exam board had also been set an unanswerable question.