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The average weight of the students in four sections A, B, C and D is 60kg. The average weight of the students in A, B, C and D individually are 45 Kg, 50 Kg, 72 Kg and 80 Kg respectively. If the average weight of the students of section A and B together is 48 Kg and that of B and C together is 60 Kg, what is the ratio of the number of students in sections A and D?

A) 12 : 7
B) 4 : 3
C) 3 : 2
D) 8 : 5

Correct Answer:


B) 4 : 3

Description for Correct answer:

Let the number of students in the sections A,B,C and D be a, b, c and d respectively. Then, total weight of students of section A = 45a
Total weight of students of section B = 50b
Total weight of students of section C = 72c
Total weight of students of section D = 80d

According to the question, Average weight of students of section A and B = 48 kg
\( \large\frac{45a + 50b}{a + b} = 48 \)

= > 45a +50b = 48a + 48b
3a = 2b
15a = 10b

And average weight of students of sections B and C = 60kg
= > 50b +72c = 60 (b +c)
= > 10b = 12c

Now average weight of students of A,B,C,D = 60 kg
45a + 50b +72c + 80d = 60(a + b + c + d)
= > 15a + 10b - 12c - 20d = 0
= > 15a = 20d
= > a : d = 4 : 3

Part of solved Average questions and answers : >> Aptitude >> Average

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