Question

A square water tank has its sides equal to $40m$. There are four semicircular grassy plots all around it. Find the cost of turfind the plots at $Rs.1.25$ per $sq.m$. (Take $\pi =3.14$)

• A. $Rs.2671$
• B. $Rs.4401$
• C. $Rs.2512$
• D. $Rs.3140$

Answer 1

The correct option is D $Rs.3140$

Given side of square tank $=40m$

Radius of semicircular plot

$=\frac{side}{2}=\frac{40}{2}=20$

Area of 1 semicicular grassy plot $=\frac{\pi r^2}{2}$

$=\frac{\pi \times {20}^2}{2}=\frac{400\pi }{2}=200\pi$

Area of 4 semicircular plot $4\times 200\pi =800\pi$ ${cm}^2$

Rate of furfind the plot

$=Rs.1.25$ per sq.m

cost of turfing the plot$=$ Area of 4 semicircular grassy plot $\times$cost

$=800\pi \times 1.25=800\times 3.14\times 1.25$

$=Rs.3140$