the mean of p,q,r,s and t is 28.if the mean of p,r and t is 24,what is the mean of q and s?

Answer :

Given 

Then mean of p , q , r , s and t is  =  28

So,

$\frac{p + q + r + s + t}{5}$ =  28

p + q  + r +  s  +   t  =  140                                                                     -------------- ( 1 )

And

Then mean of p , r  and t is  =  24

So,

$\frac{p + r+ t}{3}$ =  24

p  + r  +   t  =  72                                                                     -------------- ( 2 )

Now we subtract equation 2 from equation 1 , we get

q  +  s  = 68  , So

Mean of q and s  = $\frac{q + s}{2} = \frac{68}{2}$ =  34                                           ( Ans )