Running around a circular field – 20 laps at 12 km/h, radius 50 m: A person runs around a circular field of radius 50 m at 12 km/h. How long (in minutes) will it take to complete 20 rounds?

Introduction / Context:Time = distance / speed. For a circular track, distance per lap is circumference = 2πr. Convert units to be consistent.

Given Data / Assumptions:

• r = 50 m ⇒ circumference = 2π * 50 = 100π m.
• Laps = 20.
• Speed = 12 km/h = 12,000 m/h.

Concept / Approach:Total distance = 20 * 100π = 2000π m. Time (hours) = distance / speed. Convert to minutes by ×60.

Step-by-Step Solution:

Verification / Alternative check:220/7 ≈ 31.4286 min; matches π = 22/7 evaluation.

Why Other Options Are Wrong:110/7, 90/7, 230/7 correspond to halved/incorrect circumference or laps.

Common Pitfalls:Forgetting to multiply by laps; mixing km/h with metres.

Final Answer:110/7 min (Correction: With π = 22/7, it equals 220/7 min; select 220/7 if available. Given the provided set, 110/7 would be half the correct duration. The accurate value is 220/7 min.)