Ex 1.4, 6 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?
Marks for correct answer = +3
Marks for incorrect answer = 2
Marks for no-attempt = 0
Total marks = 20
Number of correct answers = 12
Marks for correct answers = 12 3
= 36
Also,
Marks for incorrect answer = ( 2) No. of incorrect answers
Marks for no-attempt answer = 0 No. of no-attempt
= 0
Now,
Total marks = Marks for correct answer +
Marks for incorrect answer + Marks for no-attempt
20 = 36 + ( 2) No. of incorrect answers + 0
20 = 36 + ( 2) No. of incorrect answers
20 36 = ( 2) No. of incorrect answers
16 = ( 2) No. of incorrect answers
( 16)/( 2) = No. of incorrect answers
8 = No. of incorrect answers
Number of incorrect answers = 8
So, Radhika attempted 8 questions incorrectly
Ex 1.4, 6 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. (ii) Mohini scores 5 marks in this test, though she has got 7 correct answers. How many questions has she attempted incorrectly?
Total marks = 5
Number of correct answers = 7
Marks for correct answers = 7 3
= 21
Also,
Marks for incorrect answer = ( 2) No. of incorrect answers
Marks for no-attempt answer = 0 No. of no-attempt answers
= 0
Now,
Total marks = Marks for correct answer +
Marks for incorrect answer + Marks for no-attempt
5 = 21 + ( 2) No. of incorrect answers + 0
5 = 21 + ( 2) No. of incorrect answers
5 21 = ( 2) No. of incorrect answers
26 = ( 2) No. of incorrect answers
( 26)/( 2) = No. of incorrect answers
13 = No. of incorrect answers
No. of incorrect answers = 13
She attempted 13 questions incorrectly

Made by

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.