SOLUTION: Two cities are 1580 miles apart. A plane leaves one of them traveling towards the other at an average speed of 400 miles per hour. At the same time a plane leaves the other trave

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Question 749048: Two cities are 1580 miles apart. A plane leaves one of them traveling towards the other at an average speed of 400 miles per hour. At the same time a plane leaves the other traveling towards the first at an average of 390 miles per hour. How long will it take to meet.
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
How fast are the two planes approaching eachother? That is the key concept for this problem.

A plane, 400 mph. "a" plane, 390 mph. How much time, x, so that the sum of the planes' distances be 1580 miles?
400%2Ax%2B390%2Ax=1580
%28400%2B390%29x=1580
790x=1580
x=1580%2F790=2 hours