Question 926314: Randy made a trip of 190 miles. he averages 52mph on way there on way back he averaged 56mph. Total trip took 3.5 hours, how long did travel at each rate? How do you set the problem up
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! Randy made a trip of 190 miles. he averages 52mph on way there on way back he averaged 56mph. Total trip took 3.5 hours, how long did travel at each rate? How do you set the problem up
============
There's more than 1 way, but the simplest is to use the formula
Avg = 2*52*56/(52+56) for the round trip avg speed.
Avg = 5824/108 = 1456/27 mi/hr
-----
d = r*t = (1456/27)*3.5 = 5096/27 miles RT
Distance each way = 2548/27 miles
---------
t = d/r
Going, t = (2548/27)/52 = 49/27 mi/hr
Return, t = (2548/27)/56 = 91/54 mi/hr
=========================================
I don't recommend memorizing a formula for everything, but this one is similar to parallel flows, parallel work, parallel resistors, etc. Just a factor of 2 different.
|
|
|
