SOLUTION: andy's average driving speed for a 4 hour trip was 45 miles per hour. during the first 3 hours he drove 40 miles per hour. what was his average speed for the last hour on his trip?

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: andy's average driving speed for a 4 hour trip was 45 miles per hour. during the first 3 hours he drove 40 miles per hour. what was his average speed for the last hour on his trip?      Log On


   

Question 545713: andy's average driving speed for a 4 hour trip was 45 miles per hour. during the first 3 hours he drove 40 miles per hour. what was his average speed for the last hour on his trip?
Answer by smmoore(10) About Me  (Show Source):
You can put this solution on YOUR website!
the question is asking for the average speed of the last hour. we know that the average speed for the whole 4 hour trip is 45mph, and the average speed for three of the hours is 40mph. an average is all the numbers added together, then divided by the number of numbers. \
the first 3 hours: 40+40+40 which equals 120, then to find the mean, we divide the sum by3. to see what the total sum for all 4 hrs we multiply 45(average) by 4. that equals 180.
next we do 180-120 which equals 60. so the average speed driven for the 4th hour is 60 miles per hour