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?

Explanation:

Step1: Let the number of correct answers be $x$.

The number of questions is 30, so the number of wrong answers is $30 - x$.

Step2: Calculate the score formula.

The score is given by the points from correct answers minus the points from wrong answers. A correct answer gives 4 points and a wrong answer loses 1 point, and the total score is 55. So the equation is $4x-(30 - x)=55$.

Step3: Expand and solve the equation.

Expand the left - hand side: $4x-30 + x=55$. Combine like terms: $5x-30 = 55$. Add 30 to both sides: $5x=55 + 30=85$. Divide both sides by 5: $x=\frac{85}{5}=17$.

Answer:

17