Question

in a competitive exam one mark is awarded for each correct answer while half mark is deducted for each wrong answer . jayanthi answers 120 questions and got 90 marks . how many answers did she answered correctly .​

Answer 1

Let the number of right answers be x

And the number of wrong answers be y

Then x+y =120 (total number of questions answered is 120)

Also 1*x-(1/2)*y = 90 ( one mark for right and (-1/2) for wrong answer)

So 2x - y = 180

So y = 2x - 180

Keeping this value in first equation

x + 2x - 180 = 120

3x = 120+180

3x = 300

x = 100

y =2(100) -180 =200 -180 =20

So right answers were 100 and wrong answers were 20