Question 246310: A train normally travels 60 miles at a certain speed. One day, due to bad weather, the train's speed is reduced by 10 mph so that the journey takes 3 hours longer. Find the normal speed.
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! A train normally travels 60 miles at a certain speed. One day, due to bad weather, the train's speed is reduced by 10 mph so that the journey takes 3 hours longer.
Find the normal speed.
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Let s = the normal speed
then
(s-10) = the slower speed
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Write a time equation, Time = dist/speed
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Normal time + 3 hr = Slower time
 + 3 = 
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Multiply by s(s-10), results
60(s-10) + 3s(s-10) = 60s
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60s - 600 + 3s^2 - 30s - 60s = 0
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Combine as a quadratic equation
3s^2 - 30s - 600 = 0
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Simplify, divide by 3
s^2 - 10s - 200 = 0
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Factor
(s-20)(s+10) = 0
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Positive solution;
s = 20 mph is the normal speed
:
:
Check solution, find the times of each trip
60/10 = 6 hr, slow time
60/20 = 3 hr, normal time
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diff = 3 hrs
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