Three more exam paper blunders are being investigated by the regulator, it emerged yesterday. Ofqual said it was now trying to establish how at least six mistakes in total appeared in questions on this year\'s papers – most of them at AS-level. The latest to emerge concerned a geography paper set by the Assessment and Qualifications Alliance (AQA), taken by 88,000 teenagers. They were given the wrong information in a question asking them to identify the fastest part of a flowing river. It was worth four marks towards the total of 50. AQA, Britain\'s biggest exam board, said yesterday that it would award full marks for the question to everyone who sat the paper. The head of geography at one school in southern England said: \"The question was impossible to answer correctly, in my opinion. They should cut that question from the paper. Being the first question, it really threw some of the students.\" A second mistake, also in an AQA paper – this time on computing – presented students with an arrow in a diagram that was shorter than it should have been. A spokeswoman for the board said: \"We are very sorry for these mistakes and will ensure no students will be disadvantaged as a result.\" The other slip was on a business studies GCSE paper set by the Northern Ireland exam board, the Council for the Curriculum, Examinations and Assessment. The problems came to light after Glenys Stacey, Ofqual chief executive, wrote to all UK exam boards urging them to make rigorous checks to eradicate any blunders in exams yet to be taken. She said the mistakes that had emerged so far were \"disappointing and unacceptable\". Last night, the National Union of Students wrote to Education Secretary Michael Gove urging him to hold an inquiry into the blunders. Shane Chowen, its vice-president, said: \"Those students who have been confronted with unanswerable questions may have had their confidence knocked and their performance in the rest of the exam affected. \"More needs to be done to reassure those who sat the erroneous papers that they will not have their future prospects placed in jeopardy.\" Richard Wagner, from Harlow, Essex, was one of many students concerned about the impact of the mistakes on their performances. In a blog on the BBC website he said: \"I started off really well, calculating the answer for the first question with ease, but then came the error. I didn\'t produce confident answers in the rest of the questions.\" Exam board officials acknowledged they could have created anxiety as students attempted to carry on and finish the papers. Earlier errors included a maths AS-level paper, set by the Oxford, Cambridge and Royal Society of Art board, that contained an unanswerable question worth 11 per cent of the marks for the paper. Edexcel was responsible for an AS-level biology multiple-choice question in which all four options were wrong. And an AS-level business paper set by the AQA did not include the information necessary to come up with the answer. It was worth a maximum of three marks.