SOLUTION: Ms. Munford can paint a big truck in 8 hours. Mr. Fisher can paint a big truck in 10 hours. If the big truck is already half painted before the two of them begin working on it to

Algebra ->  Rate-of-work-word-problems -> SOLUTION: Ms. Munford can paint a big truck in 8 hours. Mr. Fisher can paint a big truck in 10 hours. If the big truck is already half painted before the two of them begin working on it to      Log On


   

Question 786860: Ms. Munford can paint a big truck in 8 hours. Mr. Fisher can paint a big truck in 10 hours. If the big truck is already half painted before the two of them begin working on it together, how long will it take them to finish painting the big truck together? Give your answer in hours and round to the nearest tenth
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
ONE Job is, "paint the truck".
Ms. Mumford's rate is 1/8 jobs per hour.
Mr. Fisher's rate is 1/10 jobs per hour.
Their combined painting rate is 1%2F8%2B1%2F10=%285%2B4%29%2F40=highlight%289%2F40%29 jobs per hour.

The description tells us that HALF the job is needed with Ms. Mumford and Mr. Fisher working together. We use the uniform rate equation for this type of situation, r*t=j, t is for hours of time and j is for how many jobs.

Use the equation directly:
%289%2F40%29%2At=1%2F2
t=%281%2F2%29%2840%2F9%29
highlight%28t=20%2F9%29 hours, which you can finish in whichever way fits your objective.