Question

In the figure, there is a jogging track that has to be renovated. The cost of renovation is Rs. 15 per square meters. For the circular parts, the inner and outer radii are 6 m and 8 m respectively. Find the area highlighted in green colour (in square meters).

• A. 22
• B. 44
• C. 66
• D. 88

Answer 1

The correct option is D

88

There are two semi-circular parts (green parts) which add up to be a complete circle.

So, area of the circular part of the track = $\pi \left[\right(outerradius{)}^2-\left(innerradius{)}^2\right]$

$=\pi (8^2-6^2)=\frac{22}{7}\times 14\times 2=88m^2$

(Using identity $a^2–b^2$ = (a + b)(a - b))