# Q : 7    The inner diameter of a circular well is $\small 3.5\hspace{1mm}m$. It is $\small 10\hspace{1mm}m$ deep. Find            (ii) the cost of plastering this curved surface at the rate of Rs 40 per $\small m^2$.

Given,

Inner diameter of the circular well =  $d = \small 3.5\hspace{1mm}m$

Depth of the well = $h = 10\ m$

$\therefore$ The inner curved surface area of the circular well is $110\ m^2$

Now, the cost of plastering the curved surface per $\small m^2$ = Rs. 40

$\therefore$ Cost of plastering the curved surface of  $110\ m^2$ = $Rs.\ (110 \times 40) = Rs.\ 4400$

Therefore, the cost of plastering the well is $Rs.\ 4400$

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