Question

one car is moving on a straight road covers one third of the distance with 20km/h and the rest with 60km/h.The avg speed is

Answer 1

dist=x
$t1 = \frac{ \frac{x}{3} }{20} \\ t1 = \frac{x}{60} hrs \\ t2 = \frac{ \frac{2x}{3} }{60} \\ t2 = \frac{x}{90} hrs$
Avg speed=total dist/total time
$= \frac{x}{\frac{x}{60} + \frac{x}{90} } \\ = \frac{x}{ \frac{3x + 2x}{180} } \\ = \frac{180x}{5x}$
=36 km/hr