Question

The inner diameter of a well is 4.20 metre and it's depth is 10 metre. Find the inner surface area of the well. Find the cost of plastering it from inside at the rate Rs. 52 per sp.m.

Answer 1

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Answer 2

$\huge\underline\mathbb {SOLUTION:-}$

Answer:

• The cost of plastering is Rs 6864.

Given:

• The inner diameter of a well is 4.20 metre.
• It's depth(Height) is 10 metre.

Need To Find:

• The inner surface area of the well.
• The cost of plastering.

Explanation:

$\underline\mathsf\blue {According\:to\:the\:question\: :-}$

• $\mathsf {C.S.A\:of\:well = 2\pi rh}$

Find the Radius First:

$\underline\mathsf\pink{Formula\:used\:here\: :-}$

• $\mathsf {Radius = \frac{Diameter}{2}}$

Putting the values according to formula:

$\underline\mathsf\blue {We\:Get\: :-}$

$\implies \mathsf {Radius = \cancel{\dfrac{4.20}{2}} }$

$\implies \mathsf \green {Radius = 2.1\:m}$

Therefore, the C.S.A is:

$\implies \mathsf {C.S.A = 2\pi rh}$

$\implies \mathsf {C.S.A = 2\times \frac{22}{7}\times 2.1\times 10}$

$\implies \mathsf {C.S.A = \frac{2 \times 22 \times 2.1 \times 10}{7}}$

$\implies \mathsf {C.S.A = \frac{44 \times 21}{7} }$

$\implies \mathsf {C.S.A = \cancel{\dfrac{924}{7}} }$

$\implies \mathsf \green {C.S.A = 132\:Cm^2}$

Cost of plastering = Rate × C.S.A

• Rate = Rs 52 Per sq.m

$\mapsto$Cost of plastering = 52 × 132

$\mapsto$Cost of plastering = 6864Rs

Hence, the cost of plastering is Rs.6864.