Two cars are $$60\ \text{km}$$ away from each other and are moving towards each other at $$116\ \text{km/h}$$ and $$184\ \text{km/h}$$. How far are they from each other one and a half minutes before their collision?

The cars approach each other at a relative speed of $$116 + 184 = 300\ \text{km/h} = 5\ \text{km}$$ per minute. One and a half minutes before the collision they still have to close the gap at this rate for 1.5 minutes. So their separation then is $$5 \times 1.5 = 7.5\ \text{km}$$; the initial 60 km is not needed.