SOLUTION: There are 720 dishes that need to be rinsed. John can rinse them in 144 minutes by himself. It will take his friend Bob 72 minutes to rinse these dishes. How long will it take th

Algebra ->  Customizable Word Problem Solvers  -> Misc -> SOLUTION: There are 720 dishes that need to be rinsed. John can rinse them in 144 minutes by himself. It will take his friend Bob 72 minutes to rinse these dishes. How long will it take th      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 298531: There are 720 dishes that need to be rinsed. John can rinse them in 144 minutes by himself. It will take his friend Bob 72 minutes to rinse these dishes. How long will it take them if they rinse these 720 dishes together?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
There are 720 dishes that need to be rinsed. John can rinse them in 144 minutes by himself. It will take his friend Bob 72 minutes to rinse these dishes. How long will it take them if they rinse these 720 dishes together?
--------
John rate = 1/144 job/min
Bob rate = 1/72 job/min
-----
Together rate = 1/x job/min
===============================
Equation:
rate + rate = together rate
1/144 + 1/72 = 1/x
----
Multiply thru by 144x to get:
x + 2x = 144
3x = 144
x = 48 minutes (time for them to do the job together.
========================
Cheers,
Stan H.