Question

If a man decides to travel 80 kilometres in 8 hours partly by foot and partly on a bicycle, his speed on foot being 8 km/h and that on bicycle being 16 km/h, what distance would he travel on foot?

• A. 20 km
• B. 30 km
• C. 48 km
• D. 60 km

Answer 1

The correct option is C 48 km

Average speed = $\frac{80}{8}=10km/h$
Hence, by alligation

Ratio of time travelled by foot to that on bicycle = 6 : 2.
$\therefore$ Distance travelled by foot = $8\times 6=48km$


Alternate Approach:
Solve using options. If he travels 48 km on foot he would take 6 hours on foot. Also. in this case, he would travel 32 km on bicycle at 16 km/h - which would take him 2 hours. Thus a total of 8 hours. Option (c) satisfies the conditions of the question.