Question

In a competitive examination, one mark is awarded for each correct answer while `1/2` mark is deducted for every wrong answer. Jayanti answered 120 questions and got 90 marks. How many questions did she answer correctly?

Answer 1

Let the number of correct answers be x then the number of wrong answers be (120 – x)

Then, by given condition,

`x xx 1 - (120 - x) xx 1/2` = 90

⇒ `x - 60 + x/2` = 90

⇒ `(3x)/2` = 150

∴ x = `(150 xx 2)/5`

= 50 × 2

= 100

Hence, Jayanti answered correctly 100 questions.