SOLUTION: An airplane left Boston for St. Louis at 5pm. Two hours later, an airplane left St. Louis for Boston flying 30 mph slower than the first. The planes passed each other at 9pm. Find

Question 381098: An airplane left Boston for St. Louis at 5pm. Two hours later, an airplane left St. Louis for Boston flying 30 mph slower than the first. The planes passed each other at 9pm. Find the speeds of the planes if Boston and St. Louis are 4500 miles apart.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
An airplane left Boston for St. Louis at 5pm. Two hours later, an airplane left St. Louis for Boston flying 30 mph slower than the first. The planes passed each other at 9pm. Find the speeds of the planes if Boston and St. Louis are 4500 miles apart.
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Boston to St.Lou DATA:
time = 4 hrs; distance = x miles ; rate = d/t = x/4 mph
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St. Lou to Boston DATA:
time = 2 hrs; distance = 4500-x miles ; rate = (4500-x)/2 mph
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Equation:
rate - rate = 30 mph
(4500-x)/2 - x/4 = 30
---
2(4500-x) - x = 120
9000-2x-x = 120
9000-3x = 120
3x = 8880
x = 2960 miles
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Speed of Boston to St. Lou = 2960/4 = 740 mph
Speed of St. Lou to Boston = (4500-x)/2 = 1540/2 = 770 mph
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Cheers,
Stan H.
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