The area of a square field is 400 km2. How long will it take for a horse to run around at the speed of 20 km/h ?	Choose one:
A) 12 h  B) 10 h  C) 4 h  D) 6 h  E) none of these

Rationale: explanation area of field = 400 km 2 . then , each side of field = √ 400 = 20 km distance covered by the horse = perimeter of square field = 20 × 4 = 80 km ∴ time taken by horse = distances / peed = 80 / 20 = 4 h answer c
Answer: C