Two cars are headed for the intersection of the two roads. If
Car A is travelling south at 45 km/h and car B is travelling east
at 60 km/h, at what rate is the distance between the cars
decreasing when car A is 9 km and car B is 11 km from the
intersection? Note: Write only the numerical value of the rate, the
units are already written. Write the exact answer not the decimal
approximation (for example write 45 not 0.8).