Question

the height of a right circular cylinder with lateral surface area 792 sq cm is 21 cm find the diameter of its base

Answer 1

Hi there !!

Given,

Height of the cylinder= 21cm

Lateral surface area = 792cm²

Let the radius be ' r'

We know that ,
Lateral surface area of a cylinder = 2πrh

$792 = 2 \times \frac{22}{7} \times r \times 21$

$\frac{792 \times 7}{2 \times 22 \times 21} = r$

r = 6

Radius = 6cm

Diameter = 2 × radius = 2 × 6cm = 12cm

Answer 2

Given height of the cylinder = 21cm

CSA (lateral surface area) of the cylinder = 792cm²
Therefore 2πrh = 792cm²
→ 2×22/7×r×21 = 792cm²
→ 44×r×3 = 792cm²
→ 132×r = 792cm²
→ r = 792/132
→ r = 6cm

Hence diameter of the cylinder = 6 × 2 = 12cm ( as we know diameter is always double of radius )