Question

A hemispherical bowl is of radius 7.7 cm. It is to be painted from inside as well as outside. Find the cost (in ₹) of painting the bowl at a rate of ₹17 per 7 cm² ? (Take ∏= 22/7)

• A. 1810.16
• B. 745.36
• C. 1025.24
• D. 1620.35

Answer 1

Answer:

A. 1810.16

We need to paint the inside and outside curved surfaces of a hemispherical bowl.

Given:

• Radius (r = 7.7) cm

• Rate = ₹17 per 7 cm²

• So, rate per cm² = ₹(\frac{17}{7})

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Step 1: Total area to be painted

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

Since both inside and outside are painted:
$\text{Total area} = 2 \times 2\pi r^2 = 4\pi r^2$
$= 4 \times \frac{22}{7} \times (7.7)^2$
$= 4 \times \frac{22}{7} \times 59.29$
$= 745.64 \text{ cm}^2$

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Step 2: Cost of painting

$\text{Cost} = 745.64 \times \frac{17}{7}$
$= 1810.16$