SOLUTION: Applications of Rational Equations and Functions It takes Bill 12 hours to paint a house, and it takes John 20 hours to paint the same house. How long will it take them to pa

Algebra ->  Finance -> SOLUTION: Applications of Rational Equations and Functions It takes Bill 12 hours to paint a house, and it takes John 20 hours to paint the same house. How long will it take them to pa      Log On


   

Question 816035: Applications of Rational Equations and Functions

It takes Bill 12 hours to paint a house, and it takes John 20 hours to paint the same house. How long will it take them to paint the house if they work together? (Please show the equation and how you got the answer! THANK YOU)
Answer by TimothyLamb(4379) About Me  (Show Source):
You can put this solution on YOUR website!
b = 1 job / 12 hrs
j = 1 job / 20 hrs
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work rate for both men:
r = b + j
r = 1/12 + 1/20
r = 20/12(20) + 12/12(20)
r = 20/240 + 12/240
r = 32/240 jobs/hr
---
r = u / t
t = u / r
---
t = u / r
t = 1 job / ( 32/240 jobs/hr)
t = 240 hr / 32 job
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Answer:
t = 7.5 hr/job
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