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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.

Sagot :

MrRoyal

Answer:

(a) 12 incorrect answers

(b) 17 incorrect answers

Explanation:

Given

[tex]Correct = +4[/tex]

[tex]Wrong = -2[/tex]

[tex]Unattempted = 0[/tex]

Let the correct answer be x,

incorrect answers be y

unattempted be z

So, the equation is:

[tex]Marks = 4x - 2y + 0 * z[/tex]

[tex]Marks = 4x - 2y[/tex]

Solving (a):

Given

[tex]Marks = 20[/tex]

[tex]x = 12[/tex]

Required

Calculate y

[tex]Marks = 4x - 2y[/tex] becomes

[tex]20 = 4 * 12 - 2 y[/tex]

[tex]20 = 48 - 2 y[/tex]

Collect like terms

[tex]2y = 48 - 20[/tex]

[tex]2y = 28[/tex]

[tex]y = 12[/tex]

Solving (b):

[tex]Marks = -6[/tex]

[tex]x = 7[/tex]

Required

Calculate y

[tex]Marks = 4x - 2y[/tex] becomes

[tex]-6 = 4 * 7 - 2y[/tex]

[tex]-6 = 28 - 2y[/tex]

Collect Like Terms

[tex]2y = 28 + 6[/tex]

[tex]2y = 34[/tex]

[tex]y = 17[/tex]

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