Wheels and revolutions A car moves at 47.52 km/h. Its wheel radius is 21 cm. Approximately how many revolutions per minute does the wheel make?

Introduction / Context:
Revolutions per minute (rpm) equals the linear distance traveled per minute divided by the wheel circumference. Convert speed units to meters per minute; compute circumference from radius.

Given Data / Assumptions:

• Speed = 47.52 km/h.
• Radius r = 21 cm = 0.21 m.
• Use circumference C = 2 * pi * r; with pi ≈ 22/7 for neat arithmetic.

Concept / Approach:
rpm = (linear speed in m/min) / C.

Step-by-Step Solution:

Verification / Alternative check:
Using pi ≈ 3.1416 gives C ≈ 1.319, rpm ≈ 600.2, still rounds to 600 rpm.

Why Other Options Are Wrong:
200, 250, 300 are far too small given the circumference and speed.

Common Pitfalls:
Forgetting to convert km/h to m/min or using diameter instead of radius in the circumference formula.

Final Answer:
600 rpm