What was the average speed of the southbound train?

Question

A train leaves a station at 11am, heading north. Another train, 320 km away, leaves at the same time, heading south. The average speed of the train heading north is 20 km/hr faster than that of the train heading south. If the trains pass each other at 1.30 pm, what was the average speed of the southbound train?

Answer 1

distance=rate*time

320=(r)(2.5)+(r+20)(2.5)     11:00 am to 1:30 pm is 2.5 hours

320=2.5r+2.5r+50

320-50=5r

270=5r

r=270/5

r=54 kph is the speed of the southbound train   (answer)

r=54+20=74 kph is the speed of the northbound train