Question 245: Two planes leave O'Hare Airport in Chicago at the same time. One flies directly east at 540 mph. The other flies directly west at 720 mph. How long will it take them to be 1890 miles apart?
Found 3 solutions by ichudov, mooney, ultimate44:
Answer by ichudov(507)   (Show Source):
You can put this solution on YOUR website! After one hour, the first plane moves westward by 540 miles, and the second will move eastward by 720 miles. The distance between them (ignoring curvature of the Earth) will be 540+720 miles, that is, 1260 miles. So, the distance is incrreasing by 1260 miles per hour. To find out how long it will take them to become 1890 miles apart, you need to divide 1890 by 1260. The answer to that is left as an exercise to you.
Answer by mooney(1)  (Show Source):
Answer by ultimate44(2) (Show Source):
You can put this solution on YOUR website! ..Using SPEED(s)=DISTANCE(D)/time(t)
...Make Distance the subject
Then,let D1=st....distance eastward
And D2=st
..So substitute speed
..D1=540t and D2=720t
..because they are 1890 apart,so we say D1+D2=1890
Hence; 540t+720t=1890
..1260t=1890
..T=1890/1260
..T=1.5....meaning...one and a half hour.
ULTIMATE44
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