% In a class test (+3) marks are given for every correct answer and -2) marks are given for every
incorrect answer and no mark for not attempting any question.
6) Radhika seored 20 marks. If she has got 12 correct answers, how many questions has she
attempted incorrectly?
(in Mohini scores - 5 marks in this test though she has got 7 correct answers. How many questions
has she attempted incorrectly?
(in) Rakesh scores 18 marka by attempting 16 questions. How many questione has he attempted
correctly and how many questions has he attempted incorrectly?
Answers
Answer:
Radhika:- 8 incorrect
Mohini:- 13 incorrect
Rakesh:- 10 correct and 6 incorrect
Step-by-step explanation:
Let, Radhika incorrect answers be X
Let, Mohini incorrect answers be y
Let, Rakesh correct answers be a and incorrect answers be b
i) Marks = 20
Correct answers = 12
thus, 12 x 3 + (-2) x X = 20
36 - 2X =20
36 - 20 = 2X
16 = 2X
8 = x
So, Radhika incorrect answers are 8
ii) Marks = -5
Correct answers = 7
thus, 7 x 3 + (-2) x y = -5
21 +5 =2y
26 = 2y
13 = y
So, Mohini incorrect answers are 13
iii) Marks = 18
Total Questions = 16
thus, 3a -2b = 18 (1)
and
a + b = 16 (2)
Multiplying eq 2 by 2
2a + 2b = 32 (3)
Adding eq 1 and 3
3a - 2b=18
+2a + 2b=32
5a = 50
a = 10
Putting value of a in a + b = 16
10 + b = 16
b = 16-10
b = 6
So, Rakesh correct answers are 10 and incorrect are 6