If a boy walks from his house at 5 Km/hour, he reaches school 10 minutes early. If he walks at 3 km/hour he reaches 10 minutes late. What is the distance from his house to school?

Let us say that the actual distance between Boy’s house and school is d km and the ideal time to cover the distance is t hours. When he walks at 5 Km/hour, he reaches 10 minutes (or 1/6hours) early ⇒ d/5 = t - 1/6 ⇒ t = d/5 + 1/6 When he walks at 3 Km/hour, he reaches 10 minutes (or 1/6hours) late ⇒ d/3 = t + 1/6 ⇒ t = d/3 - 1/6 By using the above equations, d/5 + 1/6 = d/3 - 1/6 2d/15 = 1/3 d = 2.5 km Alternate method: Distance = Time gap× product of speeds/ gap of speed = 20 min×3×5/(5-3) = 20/60 hrs ×3×5/2 = 2.5 Km