Math, asked by dragoonloop, 10 months ago

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

Answered by Anonymous
1

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.

Answered by Anonymous
1

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

x = 80 - y = 72

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