Question

in an examination, a student scores 4 marks for every correct answer and losses 1 mark for every wrong answer. a students attempted all the 200 questions and scored 200 marks. find the number of questions ,he answered correctly

Answer 1

Sol:-
Let no. of correct answer = x
and let no. of wrong answer = y .
Total question attempted = 200 .
now , A. T . Q =
x+ y = 200 . (1)
and 4x + (-1y) = 200.
4x-1y = 200. (2) .
now, from (2) we get
4 x -1y = 200 .
4x = 200 + 1y .
x = ( 200+ y )÷ 4 . (3)
now , substituting (3) in (1) , we get
(200+y) ÷ 4 +y = 200
( 200+y+4y ) ÷4 = 200 . (LCM)
200+ 5y= 200×4 .
5y = 800-200
y= 600÷5
y= 120.
Then x= (200 + y) ÷ 4.
x= (200+120)÷4
x=320÷4
x= 80.
Therefore ,
No. of correct answer are 80.
No. of wrong answer are 120.