A man covers 60 km in 5 hours, partly walking at 6 km/h and partly cycling at 15 km/h. How far does he walk?

Explanation

1. 01

   His average speed is $\frac{60}{5} = 12$ km/h. Alligate the speeds over time: walking time : cycling time $= (15 - 12) : (12 - 6) = 1 : 2$.

2. 02

   He walks for $\frac{1}{3} \times 5 = \frac{5}{3}$ hours, covering $6 \times \frac{5}{3} = 10$ km.