A GMAT algebra-precalculus question about ratio

2.1k Views Asked by At

Ram committed two mistakes in an examination where all questions carried equal marks and obtained 72%. If he had attempted 4 more questions and made 3 mistakes, he would have obtained 84% marks. If there was no negative marking for wrong answers, how many questions were asked?

2

There are 2 best solutions below

2
On

If he attempted 4 and made mistakes on 3, he answered one more correctly, so 1 correct = 12% marks. So there were $100/12\approx 8$ questions on the exam.

2
On

Assume there are $x$ question in total.

Initially he answered $0.72x$ question correctly.

If he attempted $4$ more questions and made $3$ mistakes in total (the $3$ mistakes include the previous $2$ mistakes). That is he answered $3$ more questions correctly.

$$0.72x+3 = 0.84x$$

$$3=0.12x$$

$$x=\frac{3}{0.12}=25$$

I do agree that the phrasing of the question is a bit ambigious and can be improved.