SOLUTION: Two airplanes leave Boston at the same time and fly in opposite directions. If one travels at 420 miles per hour and the other at 440 miles per hour, how long will it take for them

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Question 503346: Two airplanes leave Boston at the same time and fly in opposite directions. If one travels at 420 miles per hour and the other at 440 miles per hour, how long will it take for them to be 3,440 miles apart?
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
Plane I 420 m/h
Plane II 440 m/h
Distance 3440 miles
Let time they take to be 3440 miles be x hours
Plane I distance traveled 420 x miles
Plane II distance traveled 440 x miles

Time is same
t=d/r
combined speed= 860 mph

860 x = 3440
x= 4 hours