You can put this solution on YOUR website!
Distance between City A and City B is 60 kilometres.
A driver should go from City A to City B for 1 hour.
If first 30 kilometres the driver drives with 30 km/h, what should be his speed during last 30 kilometres so he arrives in City B on time?
You can see this is not possible. The first 30 km at 30 km/hr, will take one hr
So he has 0 time to drive the 2nd 30 km