Question

The cost of fencing a circular ground at ₹120/m is ₹3,768. Find the radius of the ground.

• A. 5m
• B. 10m
• C. 15m
• D. 20m

Answer 1

Answer:

A. 5m

The fencing cost is ₹120 per metre, and the total cost is ₹3,768.

Step 1: Find the circumference

$\text{Circumference}=\frac{\text{Total Cost}}{\text{Cost per metre}}$
$=\frac{3768}{120}=31.4\text{ m}$

Step 2: Calculate the radius

$2\pi r=31.4$

Using$(\pi=\frac{22}{7}),$

$2\times\frac{22}{7}\times r=31.4$
$\frac{44}{7}r=31.4$
$r=\frac{31.4\times7}{44}$
$=\frac{219.8}{44}$
$\approx 5$

Answer

$\boxed{5\text{ metres}}$

(Using $(\pi \approx 3.14)$ gives exactly $(r=\frac{31.4}{6.28}=5) m.)$