A man runs around a circular field of radius 50 m at a speed of 12 km/h. Find the total time taken (in minutes) to complete 20 full rounds of the circular field, using pi = 22/7 for calculation consistency.

Introduction / Context:This question combines circumference of a circle with speed-time-distance conversion. You must compute the distance for one round using circumference = 2*pi*r, multiply by 20 rounds, then divide by speed. The main trick is converting 12 km/h into metres per minute so the units match metres and minutes.

Given Data / Assumptions:

• Radius r = 50 m
• Speed = 12 km/h
• Number of rounds = 20
• Circumference per round = 2 * pi * r
• Use pi = 22/7
• 1 km = 1000 m and 1 hour = 60 minutes

Concept / Approach:Total distance = (circumference) * (rounds). Time = distance / speed, with consistent units (metres and minutes). Convert speed from km/h to m/min for easy division.

Step-by-Step Solution:

Verification / Alternative check:220/7 ≈ 31.43 minutes. At 200 m/min, in about 31.43 minutes, distance covered ≈ 200 * 31.43 ≈ 6286 m, which matches 20 rounds of circumference about 314.16 m each (20 * 314.16 ≈ 6283 m). The slight difference is due to using pi = 22/7, so the result is consistent.

Why Other Options Are Wrong:

Common Pitfalls:The most common error is forgetting to convert 12 km/h into m/min and directly dividing metres by km/h. Another mistake is using diameter instead of radius in circumference, or forgetting to multiply by 20 rounds. Always keep units consistent before dividing distance by speed.

Final Answer:220/7 min