Question

A man travels $1^{st}$ $50$ km at $25km/hr$ next $40$ km with $20km/hr$ and then $90$ km at $15$ km/hr. Then find his average speed for the journey (in km/hr).

Answer 1

$1$st $50$km at $25$km/hr

Time to cover $50$km $=\frac{50}{25}=2$hrs

$2$nd $40$km at $20$km/hr

Time to cover $40$km $=\frac{40}{20}=2$hrs

$3$rd $90$km at $15$km/hr

Time to cover $90$km $=\frac{90}{15}=6$hrs

Total Distance $=50+40+90=180$km

Total Time $=2+2+6=10$hr

Average Speed $=\frac{180}{10}=18$km/hr