Question

1. A physics contest has 30 multiple-choice

questions. A correct answer gains
4 points, while a wrong answer loses
1 point. Rolly answered every question
and scored 55 points. How many
questions did he answer correctly?

Answer 1

He gave 17 answers correctly.

Explanation:

Given: Correct answer gains 4 points and incorrect answer loses 1 point.

Let the no. of correct answer be x and incorrect answers be y.

So,

no. of questions is

30 = x + y

& correct answer is

55 = (4 × x )+ (-1 × y )

55 = 4x - y

By Elimination Method,

55 + 30 = x + 4x + y - y

85 = 5x

17 = x