Question:
The area of a square field is 60025 m2. A man cycles along its boundary at 18 km/h. In how much time will he return to the starting point?
Solution:
Area of the square field $=60025 \mathrm{~m}^{2}$
Length of each side of the square field $=\sqrt{60025}=245 \mathrm{~m}$
Perimeter of the field $=4 \times 245=980 \mathrm{~m}$
$=\frac{980}{1000} \mathrm{~km}$
The man is cycling at a speed of 18 km/h.
Time $=\frac{\text { Distance travelled }}{\text { Speed }}$
$=\frac{980 / 1000}{18}$
$=\frac{980}{1000 \times 18} \mathrm{hr}$
$=\frac{980 \times 60 \times 60}{18000} \mathrm{sec}$
$=98 \times 2 \mathrm{sec}$
$=196 \mathrm{sec}$
$=3 \mathrm{~min} 16 \mathrm{sec}$