Question

One third of a certain journey is covered at the rate of 25km/ hour, one-fourth at the rate of 30km/hour and the rest at 50km/hour. The average speed for the whole journey is

Answer 1

Sav = d/d (1/3*25+1/4*30+5/12*50)=1/(1/75+1/120+5/600)=600/(8+5+5)=600/18=100/3 km/h