Question

a plane traveling at 400 mph leaves the philadelphia airport at 1pm heading due east. two hours later a second plane traveling at 600 mph leaves the airport heading in the same direction. at what time does the second plane overtake the first?

Answer 1

When the 2nd overtakes the first, they will have travelled the same distance:

let the time of the first plane since 1:00 pm be t hrs
distance covered by first plane = 400t miles

let the time of the 2nd plane be t-2 hrs
distance covered by 2nd plane = 600(t-2)

400t = 600(t-2)
400t = 600t - 1200
-200t = -1200
t = 6

so time since 1:00 is 6 hrs, or the time will be 7:00 pm