Question

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:
1) 20 kg
2) 31 kg
3) 26 kg
4) 17 kg

Answer 1

2) 31.....................

Answer 2

The average weight of A,B and C is 45 kg. Then total weight of them is 45*3=135 kgs.
Similarly total weight of A and B is 40*2=80 kgs. and total weight of B and C is 43*2=86 kgs.
Now, we can write
A+B+C=135 -------(1)
A+B=80------------(2)
B+C=86------------(3)
subtracting (2) and (3) from (1) we get,
C=55 and A=49
Then weight of B is :
135-(49+55)=135-104=31 kgs.