SOLUTION: A man drove the first 75 miles of a trip at an average of 50mph. He then drove the next 150 miles at an average of 60 mph. What was his average speed in mph for the trip?

Question 334172: A man drove the first 75 miles of a trip at an average of 50mph. He then drove the next 150 miles at an average of 60 mph. What was his average speed in mph for the trip?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
A man drove the first 75 miles of a trip at an average of 50mph.
He then drove the next 150 miles at an average of 60 mph.
What was his average speed in mph for the trip?
:
Let a = average speed for the trip
:
Write a time equation, time = dist/speed
Total trip dist = 75 + 150 = 225
:
50mph time + 60mph time = total time
+ =
:
Multiply by 300a to get rid of the denominators, results
6a(75) + 5a(150) = 300(225)
:
450a + 750a = 67500
:
1200a = 67500
a =
a = 56.25 mph is the average speed
:
:
See if that is true, find the times:
+ =
1.5 + 2.5 = 4
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