The inner diameter of a circular well is 3.5 m  . It is 10 m  deep. What is the cost of plastering its inner curved surface at Rs. 4 per square meter?

# The inner diameter of a circular well is  . It is  deep. What is the cost of plastering its inner curved surface at Rs. 4 per square meter?

1. A
Rs. 400
2. B
Rs. 440
3. C
Rs. 800
4. D
Rs. 880

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### Solution:

It is given that,
The inner diameter of the well = 3.5m  and height of well = 10m.
Now,
.
Thus, the radius of the well,
The area of curved surface of well,
CSA$=2\mathit{\pi rh}$
$⇒$CSA$=2×\frac{22}{7}×\frac{3.5}{2}×10$
$⇒$CSA$=110{m}^{2}$
We know the price of plastering .
Thus, the price of plastering the area's curved inner surface is,
Thus, plastering the interior curved surface costs Rs.440.
Therefore, the correct option is 2.

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