Question

The radii of the bases of two cylinders are in the ratio 3 : 5 and their heights are in the ratio 2 : 3. The ratio of their curved surfaces will be 

(a) 2 : 5 

(b) 2 : 3 

(c) 3 : 5 

(d) 5 : 3

Answer 1

(a) 2 : 5

Ratio of curved surfaces = \(\frac{2πr_1h_1}{2πr_2h_2} = \big(\frac{r_1}{r_2}\big)\times\big(\frac{h_1}{h_2}\big)\)

= \(\frac35\times\frac23=\frac25=\) 2 : 5