The ratio of the total surface area to the lateral surface area of a cylinder with base radius 80 cm and height 20 cm is
Question:

The ratio of the total surface area to the lateral surface area of a cylinder with base radius 80 cm and height 20 cm is
(a) 2 : 1
(b) 3 : 1
(c) 4 : 1
(d) 5 : 1

Solution:

(d) 5 : 1

Ratio of the total surface area to the lateral surface area $=\frac{\text { Total surface area }}{\text { Lateral surface area }}$

$=\frac{2 \pi r(h+r)}{2 \pi r h}$

$=\frac{h+r}{h}$

$=\frac{(20+80)}{20}$

$=\frac{100}{20}$

$=\frac{5}{1}$

$=5: 1$

Hence, the required ratio is 5:1.