Question

The difference between the inner surface area and the outer surface area of a hollow cylinder having height 7 cm and inner and outer radius of 3 cm and 4 cm respectively is:

• A. $22c{m}^2$
  
• B. $88c{m}^2$
  
• C. $44c{m}^2$
  
• D. $42c{m}^2$

Answer 1

The correct option is C

$44c{m}^2$

Given: Outer radius = 4 cm
Inner radius = 3 cm
Height of the cylinder = 7 cm

Outer surface area = $2\pi r_{2}h$
$=2\times \frac{22}{7}\times 4\times 7=176c{m}^2$

Inner surface area = $2\pi r_{1}h$
$=2\times \frac{22}{7}\times 3\times 7=132c{m}^2$

Difference between them = $176-132=44c{m}^2$