Question

The cost of fencing a circular field at the rate of Rs. 12 per meter is Rs. 1320. The field is to be ploughed at Rs. 2 per $m^2$, then cost of ploughing is: $(\text{use}\pi =\frac{22}{7})$

• A. $Rs.3850$
• B. $Rs.1925$
• C. $Rs.660$
• D. $Rs.2585$

Answer 1

The correct option is B $Rs.1925$

Given that at a rate of $Rs.12$ per meter, the cost of fencing the circular field is $Rs.1320$

Hence, circumference of the field $=\frac{1320}{12}=110m$
We know that, circumference of a circle is $2\pi r$

$\therefore 2\pi r=110$

$\Rightarrow 2\times \frac{22}{7}\times r=110$

$\Rightarrow r=\frac{35}{2}m$

We also know that the area of a circle is $\pi r^2$

So, area of the field $=\frac{22}{7}\times \frac{35}{2}\times \frac{35}{2}=\frac{1925}{2}{m}^2$

Given that the cost of ploughing one $m^2$ area is $Rs.2$.

Hence, cost of ploughing the field at $Rs.2$ per $m^2=\frac{1925}{2}\times 2=Rs.1925$.

Hence, option B is correct.