At 1000 am two planes leave an airport If the northbound pla

At 10:00 a.m. two planes leave an airport. If the northbound plane flies at 280 mph and the southbound at 320 mph, at what time will they be 1,000 miles apart?

Solution

280t+320t=1,000
600t=1,000
t=1,000/600
t=1.667 hours or 1 hr. & 40 min. they will be 1,000 miles apart.
10:00+1:40=11:40 is the time.