In a multiple-choice examination of 25 questions, four marks are given for each correct answer and two marks are deducted for each wrong answer.
One mark is deducted for any question which is not attempted. A candidate attempts q questions and gets c correct.
(i) Write down an expression for the candidate’s total mark in terms of q and c.
(ii) James attempts 22 questions and scores 55 marks.
Write down and solve an equation for the number of questions which James gets right.
My answer:
Total mark = 4c - 2 (25 - c) - (25 - q)
= 4c - 50 + 2c - 25 + q
= 6c - 75 + q
I went on to answer part (ii), but according to the answers I had already gotten the first part wrong, so inevitably got the rest wrong too. Can I have some help with where I went wrong?
One mark is deducted for any question which is not attempted. A candidate attempts q questions and gets c correct.
(i) Write down an expression for the candidate’s total mark in terms of q and c.
(ii) James attempts 22 questions and scores 55 marks.
Write down and solve an equation for the number of questions which James gets right.
My answer:
Total mark = 4c - 2 (25 - c) - (25 - q)
= 4c - 50 + 2c - 25 + q
= 6c - 75 + q
I went on to answer part (ii), but according to the answers I had already gotten the first part wrong, so inevitably got the rest wrong too. Can I have some help with where I went wrong?