Question

4. In a competitive examination, (+4)

marks are given for every correct
answer, (-2) marks are given for every
incorrect answer and 0 marks for not
attempting the question.
a) Ruchi scored 20 marks. If she
has got 12 correct answers, how
many questions has she attempted
incorrectly?
b) Rohit scored(-6 )marks in this test .Through he has got 7 correct answers .How many questions has he attempted incorrectly.

Answer 1

(a) 12 incorrect answers

(b) 17 incorrect answers

Step-by-step explanation:

Given

`Correct = +4`

`Wrong = -2`

`Unattempted = 0`

Let the correct answer be x,

incorrect answers be y

unattempted be z

So, the equation is:

`Marks = 4x - 2y + 0 * z`

`Marks = 4x - 2y`

Solving (a):

Given

`Marks = 20`

`x = 12`

Required

Calculate y

`Marks = 4x - 2y` becomes

`20 = 4 * 12 - 2 y`

`20 = 48 - 2 y`

Collect like terms

`2y = 48 - 20`

`2y = 28`

`y = 12`

Solving (b):

`Marks = -6`

`x = 7`

Required

Calculate y

`Marks = 4x - 2y` becomes

`-6 = 4 * 7 - 2y`

`-6 = 28 - 2y`

Collect Like Terms

`2y = 28 + 6`

`2y = 34`

`y = 17`