A cyclist completes one round of a square field in 18 seconds while travelling…

Concept

For uniform motion, distance equals speed multiplied by time. For a square, perimeter equals four times its side length, so side length equals perimeter divided by 4.

Application

1. Distance covered in one round = 30 × 18 = 540 m.

2. One complete round traces the boundary of the square, so its perimeter is 540 m.

3. Side length = perimeter ÷ 4 = 540 ÷ 4 = 135 m.

Cross-check

A square with side 135 m has perimeter 4 × 135 = 540 m. At 30 m/s, covering 540 m takes 540 ÷ 30 = 18 seconds, which reproduces the given time.

Result

Therefore, the side length of the field is 135 m.