SOLUTION: Felicia and Rachelle are students in Mr. Johnston's Math 12 class. They got behind on their workcand need to finish seven assignments on the weekend. It would take Felicia 4 hours

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Question 121862: Felicia and Rachelle are students in Mr. Johnston's Math 12 class. They got behind on their workcand need to finish seven assignments on the weekend. It would take Felicia 4 hours to finish the work by herself. It would take Rachelle 5 hours. If they worked together, how long would it take them to finish the work?
(answer in hours and minutes please:] )
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
t would take Felicia 4 hours to finish the work by herself. It would take Rachelle 5 hours. If they worked together, how long would it take them to finish the work?
(answer in hours and minutes please:] )
:
Let t = time required if they work together:
:
Let the completed work = 1
:
t%2F4 + t%2F5 = 1
:
Multiply equation by 20 to get rid of the denominator
20*t%2F4 + 20*t%2F5 = 20(1)
Cancel out the denominators and you have:
:
5t + 4t = 20
9t = 20
t = 20%2F9
t = 2.222 hr
:
Change .222 hrs to minutes: .222 * 60 = 13.3 minutes
2 hrs 13 min working together:
:
:
Check solution using the decimals
2.222/4 + 2.222/5 =
.5555 + .4444 = .9999 ~ 1