Question

In a class test (+3) marks are given for every correct answer and (–2) marks are given for every incorrect answer and no marks for not attempting any question. (i) Radhika scored 20 marks. If she has got 12 correct answers, how many questions has she attempted incorrectly? (ii) Mohini scores (–5) marks in this test, though she has got 7 correct answers. How many questions has she attempted incorrectly?
SCERT Class 7 Telangana, Maths Chapter 1 Integers

Answer 1

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Let the number of correct answers in each case be x.
Let the number of incorrect answers in each case be y.
So, the total marks for correct answers will be 3x and the marks subtracted for incorrect answers will be -2y
(i) 3x-2y=20
x is given as 12
So, 3×12-2y=20
36-2y=20
2y=36-20
=16
y=8
So Radhika gave 8 incorrect answers.

(ii) 3x-2y=-5
x is given as 7
3×7-2y=-5
21-2y=-5
2y=21+5
=26
y=13
So Mohini gave 13 incorrect answers.

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