A tourist covers half of his journey by train at 60 km/h, half of the…

Method: compute average speed as total distance divided by total time.

Take the total journey distance as 1 unit. Distances covered:

• By train: 1/2 of the distance at 60 km/h => distance = 0.5

• By bus: half of the remainder = 1/4 of total at 30 km/h => distance = 0.25

• By cycle: remaining 1/4 at 10 km/h => distance = 0.25

Compute times for each part:

• Time by train = distance/speed = 0.5 ÷ 60 = 1/120 hours

• Time by bus = 0.25 ÷ 30 = 1/120 hours

• Time by cycle = 0.25 ÷ 10 = 1/40 hours

Total time = 1/120 + 1/120 + 1/40 = 5/120 = 1/24 hours.

Average speed = total distance ÷ total time = 1 ÷ (1/24) = 24 km/h.