The average weight of A, B and C is 45 kg. If the average weig | MHSS STUDENT LEARNING SYSTEM

The average weight of A, B and C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, then the weight of B is:
A. 17 kg
B. 20 kg
C. 26 kg
D. 31 kg
Answer: D

Let A, B, C represent their respective weights. Then,
A + B + C = 45
3
A + B + C = (45*3)=135 (¡)

A + B = (40 x 2) = 80 .... (ii)
B + C = (43 x 2) = 86 ....(iii)

Adding (ii) and (iii), we get: A + 2B + C = 166 .... (iv)

Subtracting (i) from (iv), we get : B = 31.
B's weight = 31 kg.