On a 60 km straight road, a bus travels the first 30km with a uniform speed of `30kmh^(-1)`. How fast must the bus travel the next 30 km so as to have average speed of `40kmh^(-1)` for the entire tirp?

Explanation

`V_(avg)=(S_(1)+S_(2))/(t_(1)+t_(2))=(S+S)/(S((1)/(V_(1))+(1)/(V_(2))))=(2V_(1)V_(2))/(V_(1)+V_(2))`
or `40=(2xx30xxV_(2))/(V_(1)+V_(2))impliesV_(2)=60kmh^(-1)`