Question

In a competitive examination 1 mark is awarded for each correct answer while 1/2 mark is deductedfor every wrong answer. jayanti answered 120 question and got 90 marks . how many question she answered correctly?

Answer 1

she answered 100 questions correctly and 20 of her answers were incorrect.

let x denote the number of questions she answered correctly ,then number of questions she answered incorrect = 120 - x..
then,
x×1 - 1/2×(120- x) = 90
from here x = 100