A cyclist goes from one town to another at 45 km/h and comes back by the same road at 90 km/h. What is the average speed for the whole journey?

💡 Solution & Explanation

Average speed = total distance ÷ total time, not the average of the two speeds. For equal distances, average speed = 2ab ÷ (a + b) = 2 × 45 × 90 ÷ (45 + 90) = 60 km/h. The simple average (67.5 km/h) is wrong because more time is spent at the slower speed.