(Solved): Two straight highways, one running west to east and the other running north to south meet at an int ...

Two straight highways, one running west to east and the other running north to south meet at an intersection. Car A is on the east-west highway 300 metres east of the intersection and is travelling east at $60\mathrm{km}/\mathrm{h}$. Car B is on the north-south highway 400 metres south of the intersection and is travelling north at $75\mathrm{km}/\mathrm{h}$. At what rate is the distance between the two cars changing at this moment? Hint: There are 1000 metres in one kilometre. the distance is deceasing at a rate of $48\mathrm{km}/\mathrm{h}$ the distance is increasing at a rate of $48\mathrm{km}/\mathrm{h}$ the distance is increasing at a rate of $24\mathrm{km}/\mathrm{h}$ the distance is deceasing at a rate of $12\mathrm{km}/\mathrm{h}$