A car travels 240 km in 4 hours. What is its average speed?

💡 Speed = Distance ÷ Time.

A train running at 72 km/h crosses a 200 m long platform in 15 seconds. What is the length of the train?

💡 Convert km/h to m/s (× 5/18). Train + platform = total distance.

A man covers a distance of 60 km at 30 km/h and returns at 60 km/h. Find his average speed for the whole journey.

💡 For equal distances, average speed = 2uv/(u+v) — harmonic mean, not arithmetic.