If P travelled the first half of a journey at 40 km/hr and the remaining distance at 50 km/hr, what is the average speed of his travel? A. 44.44 km/hr B. 53.33 km/hr C. 45 km/hr D. 60 km/hr

When equal distances are covered at speeds a and b, the average speed is the harmonic mean, 2ab/(a + b). So the average = 2 × 40 × 50/(40 + 50) = 4000/90 ≈ 44.44 km/h. (The simple average, 45, is wrong because more time is spent at the slower speed.)