### If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55, 60, then the average marks of all the students is:

A. 53.33

B. 54.68

C. 55

D. None of these

$\begin{array}{l}\therefore\text{Required average }\\ =\Large\frac{55\times50+60\times55+45\times60}{55+60+45}\\ =\Large\frac{2750+3300+2700}{160}\\ =\Large\frac{8750}{160}\\ =54.68\end{array}$