The Examinations Authority has apologised to students for a typing error in the pure mathematics A-level paper that slipped through despite a system of multiple checks. Almost all the 9,200 students who sat the examination on Friday chose to answer question No 8, a calculus problem in which (6-x) was mistyped as (x-6) in an equation. Senior officials from the authority said they regretted the incident and that a committee would be set up to investigate what went wrong. 'It's true that the question was printed wrong,' said the body's chairman, Joseph Chow Ming-kuen. 'For some unknown reason it was not spotted during the checking process. 'I would like to take the opportunity to express our regret to the students.' To reassure students who were thrown by the mistake and perhaps wasted time, they will be marked on how they tackled the question rather than whether they got the answer right. Also, as it was the second part of the examination, performance in the first paper will be used as a guide to marking the second paper. The authority said a re-sit would only be called as a last resort. The committee is expected to be formed later this week to review the checking system, which has been in place since 1977. It is believed that several people could be responsible as the exam paper was drafted by a team of six or seven. Another team of proof-readers was designated to make sure the paper was free of mistakes before the principal question setter went through it again. An independent assessor not involved in any of the previous steps was appointed to go over all the questions as a final step. A message posted on the Internet by a student read: 'Even if the question is cancelled or the exam authority gives me the full mark on it, I still think this is unfair. I spent so much time on that question and had little time left to finish the paper.' Earlier the authority had to adjust the marking scheme for a history paper in which the Chinese version of the paper mis-typed the year 1919 as 1900.