SOLUTION: You are driving a transport truck on a 300 mile trip. You drive at 60 miles per hour for the first 100 miles, then at 65 miles per hour for the last 200 miles. What is your average

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Question 574655: You are driving a transport truck on a 300 mile trip. You drive at 60 miles per hour for the first 100 miles, then at 65 miles per hour for the last 200 miles. What is your average speed for the entire trip?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
You are driving a transport truck on a 300 mile trip.
You drive at 60 miles per hour for the first 100 miles, then at 65 miles per hour for the last 200 miles.
What is your average speed for the entire trip
:
let a = average for the entire trip
:
Write a time equation, time = dist/speed
:
100%2F60 + 200%2F65 = 300%2Fa
Multiply by 3900a, (60*65)
3900a*100%2F60 + 3900a200%2F65 = 3900a*300%2Fa
cancel the denominators
65a(100) + 60a(200) = 3900(300)
6500a + 12000a = 1170000
18500a = 1170000
a = 1170000%2F18500
a = 63.24 mph is the average speed
:
:
Check solution using decimals
100/60 = 1.67 hrs
200/65 = 3.08
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300/63.24 = 4.74, close enough to check it.