Question

The average weight of the students
in four sections A, B, C and D is 55 kg. The average weights
of the students A B C and D are 45
kg, 40 kg, 75 kg and 85kg respectively. If the average weight of the students of section A and D
together is 65 kg and that of B and
D together 55 kg, then what is the
ratio of the number of students in A and C?​

Answer 1

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

45a+50ba+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

Answer 2

Answer:

It's too difficult , sorry but I think you have your answer