Question

The slant height and base diameter of a conical tomb are 25 m and 14 m respectively. Find the cost of white-washing its curved surface at the rate of Rs.210 per 100 sq.m.​

Answer 1

Given :

• Slant height of conical tomb = 25m
• Base diameter of conical tomb = 14m
• Rate of white washing = ₹210 per 100m²

To find :

Cost of white washing curved surface of tomb

Formula used :

Curved surface area of cone = πrl

Here,

• r = base radius of cone
• l = slant height of cone

Solution :

First of all we need to find base radius of conical tomb,

Radius = diameter ÷ 2

➝ Radius = 14m ÷ 2

➝ Radius = 7m

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Now , CSA of conical tomb = π(7m)(25m)

$\sf \implies \: CSA \: of \: conical \: tomb \: = \: \dfrac{22}{7} \times 7m \times 25m \\ \\ \sf \implies \: CSA \: of \: conical \: tomb \: = \: 22 \times 25 \: {m}^{2} \\ \\ \sf \implies \: CSA \: of \: conical \: tomb \: = \: 550 \: {m}^{2}$

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Cost of white washing

➝ Cost of white washing 100m² = ₹210

➝ Cost of white washing 1m² = ₹210 ÷ 100

➝ Cost of white washing 1m² = ₹2.1

➝ Cost of white washing 550m² = ₹2.1 × 550

➝ Cost of white washing = ₹1155

ANSWER : ₹1155