SOLUTION: Malik drove his car for 45 miles at an average speed of r miles per hour. On the return trip, traffic has increased, and Malik's average speed is 3/4r. The round trip took a tota

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: Malik drove his car for 45 miles at an average speed of r miles per hour. On the return trip, traffic has increased, and Malik's average speed is 3/4r. The round trip took a tota      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 736464: Malik drove his car for 45 miles at an average speed of r miles per hour. On the return trip, traffic has increased, and Malik's average speed is 3/4r. The round trip took a total of 1 hour and 45 minutes. Find the average speed for each portion of the trip.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Malik drove his car for 45 miles at an average speed of r miles per hour.
On the return trip, traffic has increased, and Malik's average speed is 3/4r.
The round trip took a total of 1 hour and 45 minutes.
Find the average speed for each portion of the trip.
:
Change 1 hr 45 min to 1.75 hrs, Change 3/4r to .75r
:
Write a time equation, time = dist/speed
:
45%2Fr + 45%2F%28.75r%29 = 1.75
multiply equation by .75r, to clear the denominators
.75(45) + 45 = 1.75(.75r)
33.75 + 45 = 1.3125r
78.75 = 1.3125r
f = 78.75/1.3125
r = 60 mph
and
.75(60) = 45 mph on the return trip
:
:
Check this find the actual time each way
45/60 = .75 hr
45/45 = 1 hr
---------------
total time 1.75 hrs