Question

The inner diameter of a circular well is $3.5$ m. It is $10$ m deep. Find the cost of plastering this curved surface at the rate of Rs. $40$ per m${}^2$.

• A. Rs. $4000$
• B. Rs. $4400$
• C. Rs. $4500$
• D. Rs. $4800$

Answer 1

Answer: (B)

Rs. $4400$

Given diameter of well is $3.5$ m and depth is $10$ m and cost of plastering is Rs. $40$ per sq m.

Then radius of well $=\frac{3.5}{2}=1.75$ m

And height of well $=10$ m

Then curved surface area of well $=$ $2\pi rh=2\times \frac{22}{7}\times 1.75\times 10$

$=$ $2\times 22\times 0.25\times 10=110m^2$

Then cost of plastering curved surface area $=$ $110\times 40=$ Rs. $4400$.