Carcass wrote:
The scores reported for a certain multiple-choice test were derived by subtracting 1/3 of the number of wrong answers from the number of right answers. On a 40-question test, if none of the questions was omitted and the score reported was 20, how many wrong answers were there?
(A) 5
(B) 10
(C) 15
(D) 25
(E) 30
Kudos for the right answer and explanation
Question part of the project GRE Quantitative Reasoning Daily Challenge - (2021) EDITIONGRE - Math BookLet the number of right answers be R and wrong answers be W
Given: Score = 20 = \(R - \frac{W}{3}\)
Also, R + W = 40
Plug R = 40 - W in the above equation
\(20 = (40 - W) - \frac{W}{3}\)
\(60 = 120 - 3W - W\)
\(4W = 60\)
\(W = 15\)
Hence, option C