posted by Jane on .
Two trains, one express and one local, leave Indianapolis at noon and head for Chicago 220 miles away. The express travels twice as fast as the local and arrives 2 hours ahead of the local. Find the speed of each train.
If the slow train's speed is s, then recall that time = distance/ speed:
220/s = 220/(2s) + 2
s = 55
so, the slow train travels 55 mph, the fast 110 mph.
slow takes 220/55 = 4 hours
fast takes 220/110 = 2 hours, arriving 2 hours earlier