Question

A police officer is on the RTA red line train on the way home from the airport. The tracks run near a road, W 150th, that happens to be perfectly North-South. A black convertible Audi on the W150 is traveling directly north and the police officer wonders if it is speeding in a school zone (speed limit 20mph). The officer can see the conductor’s control panel: the train is traveling approximately northeast at 26 mph. The officer walks backward relative to the train at 4 ft/sec. If the moving officer perceives the Audi to move directly west at 11 mph, how fast is the Audi traveling?

Answer 1