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.
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