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:

Answer 1

Average= Sum of observation/ Total number of observation

# Average of A,B,C = $\frac{A+B+C}{3}$ = 45

from above case,        A+B+C= 45×3=135        ...................(1)

#Average of A, and B =   $\frac{A+B}{2}$ =40

 from above case,        A+B = 80   ........................................(2)

#Average of B and C =  $\frac{B+C}{2}$ =43

from above case,        B+C = 86 ...........................................(3)

From .....(1)

A+B+C = 135

we know from...(2)  A+B=80

A+B+C =135
80+C=135

*C=135-80=55


From .....(1)

A+B+C = 135

From.....(3)
B+C= 86

A+B+C=135
A+86= 135
*A=135-86=49


From ...(1)
A+B+C=135

We know now from above, A=49 and C =55
putting the value in......(1)

A+B+C =135
49+B+55 =135
104+B=135

*B=135-104 =31

Hence this way we got all the values of A, B and C.             :)