In an examination one mark is awarded for every correct answer while 1/2
mark is deducted for
every wrong answer .Suraj answered 80 questions and got 60 marks .How many questions did he answer correctly.
plz write full solution
Answers
Total answers = 120
Let the number of correct answers = x
number of wrong answers = (120-x)
Marks awarded for each right answer = 1
then Marks awarded for x right answer = x × 1 = x marks
Marks deducted for each wrong answer = 0.5
then marks deducted for (120-x) right answers = (120-x) × 0.5 = 60 - 0.5x
So she will get= marks awarded for right answer - marks deducted for wrong answer
= x - (60-0.5x)
= x - 60 + 0.5x
= 1.5x - 60
And she has got = 90 marks
So
1.5x - 60 = 90
⇒ 1.5x = 90 + 60
⇒ 1.5x = 150
⇒ x = 150/1.5
⇒ x = 100
So she did 100 questions correctly.
Answer:
72
Step-by-step explanation:
Mistake in question: Marks deducted for every wrong answer = 1(1/2) = 3/2
Let number of correct answers be = x
Let number of wrong answers be = y
.°. x + y = 80 (he answered 80 questions)
x = 80 - y ...(1)
Also, according to given information:
x(1) + y(-3/2) = 60 (he has got 60 marks only)
x - 3y/2 = 60
2x - 3y = 120 ...(2)
(1) in (2):
160 - 2y - 3y = 120
40 = 5y
y = 8