Question

A hemispherical bowl with diameter 14 cm has to be painted inside and outside. How much it will be charged at the rate of ₹20 per 40 cm² ?

• A. ₹154
• B. ₹616
• C. ₹308
• D. ₹224

Answer 1

Answer:

C. ₹308

Diameter = 14 cm
Radius ( r = 7 ) cm

Since the bowl is hemispherical and needs to be painted inside and outside, we paint:

• Inner curved surface area

• Outer curved surface area

Curved surface area of a hemisphere = ( 2\pi r^2 )

So, total area to be painted:

$2 \times (2\pi r^2) = 4\pi r^2$
$= 4\pi (7^2)$
$= 4\pi (49)$
$= 196\pi$
$Using ( \pi = \frac{22}{7} ):$

$196 \times \frac{22}{7}$

$= 28 \times 22$
$= 616 \text{ cm}^2$

Cost Calculation

Rate = ₹20 per 40 cm²

Cost per 1 cm² =$\frac{20}{40}$= ₹0.5

Total cost:

$616 \times 0.5$ = ₹308

Final Answer: ₹308