1)

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

A) 53.33

B) 54.68

C) 55

D) None of these

Required avrage = $\frac{55\times50+60\times55}{55+60+45}$
$=\frac{2750+3300+2700}{160}=\frac{8750}{160}=54.68$