### The average height of 30 boys out of a class of 50 is 160 cm. If the average height of the remaining boys is 165 cm, the average height of the whole class (in cm) is :

A. 161

B. 162

C. 163

D. 164

Average height of the whole class $\begin{array}{l}=\Large\frac{30\times160+20\times165}{50}\\ =\Large\frac{3\times160+2\times165}{5}\\ =96+66\\ =162\mathrm{~cm}\end{array}$