Question

The radius of a circular pond is 10 m. Find the cost of cementing a circular platform of width 4 m around the pond at the rate of ₹30 per square metre.

• A. $601.71m^2$
• B. $398.57m^2$
• C. $301.71m^2$
• D. $465.28m^2$

Answer 1

The correct option is C $301.71m^2$

The radius of the pond = r = 10 m
The radius of the outer circle = R = 10 + 4 = 14 m
Area of the circular platform around the pond = π ($R^2-r^2$)
Cost of cementing the above area = Area of the circular platform around the pond x Unit cost
= $\frac{22}{7}({14}^2-{10}^2)$ x $30$
= $\frac{22}{7}(196-100)$ x $30$
= $\frac{22}{7}\left(96\right)$ x $30$
= Rs. 9051.43