Question

198. The internal and external radii of a hollow cylinder are 4 cm and 6 cm respectively. What is the ratio of its internal surface area to its external surface area? a. 4:9 b. 2:3 c. 3:4 d. 9:4

Answer 1

$<i><b><u>hey mate$
Since the cylinder is hollow, we get the area of the curved surface.

The internal surface area :
Let the height of the cylinder be h.

r = 4

Curved surface area = πDh

πD = 3.142 × 8 = 25.136

C. A = 25.136h

The external surface area :
The height = h

D = 6 × 2 = 12`

C. A = 12 × 3.142 × h = 37.704h

Internal surface to external surface :

25.136 /37.704

= 25/38

Approximately :

25 : 38