Question

A window is in the shape of a semicircle having its diameter as $140cm$. Find the cost of framing the window at the rate of $Rs.5percm$. Also, find the cost of putting glass at the rate of $Rs.31perc{m}^2$.

Answer 1

Radius of semicircle $=\frac{d}{2}=\frac{!40}{2}=70cm$

Perimeter of semicircle $=\pi r=\frac{22}{7}\times 70=220cm$

Rate of framing $=Rs.5\text{per cm}$

Therefore,

Cost of framing the window $=5\times 220=Rs.1100$

Also,

Area of semicircle $=\frac{1}{2}\pi r^2=\frac{1}{2}\times \frac{22}{7}\times 70\times 70=7700{cm}^2$

Rate of putting glass $=Rs.31\text{per}{cm}^2$

Therefore,

Cost of putting glass $=31\times 7700=Rs.238700$