Question

Area of the base of a right circular cone is 308 cm² and its height is 7√2 cm. Find its curved surface area (in cm²). (Use ∏= 22/7)

• A. 308√3
• B. 320√3
• C. 308√2
• D. 325√5

Answer 1

Answer:

C. 308√2

Given:

Area of base of cone = 308 cm²
Height ( h = 7\sqrt{2} ) cm
$( \pi = \frac{22}{7} )$

Step 1: Find the radius

Area of base = ( \pi r^2 )

$\frac{22}{7} r^2 = 308$

$r^2 = \frac{308 \times 7}{22}$
$r^2 = 98$

$r = 7\sqrt{2}$

Step 2: Find the slant height ( l )

$l = \sqrt{r^2 + h^2}$
$l = \sqrt{98 + 98}$

$l = \sqrt{196} = 14$

Step 3: Curved Surface Area (CSA)

$CSA = \pi r l$

$= \frac{22}{7} \times 7\sqrt{2} \times 14$
$= 22 \times 14\sqrt{2}$
$= 308\sqrt{2}$