SOLUTION: Larry takes 2 hours to paint a house.Willy takes 4 hours to paint the same house.David takes 8 hours to paint that house.How long would it take them to paint the house, working tog

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Question 107435: Larry takes 2 hours to paint a house.Willy takes 4 hours to paint the same house.David takes 8 hours to paint that house.How long would it take them to paint the house, working together?
Found 2 solutions by josmiceli, edjones:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The sum of their rates of painting is the rate of all three
together
(1 house/2 hrs) + (1 house/4 hrs) + (1 house/8 hours) = (1 house)/x hours)
1/2 + 1/4 + 1/8 = 1/x
4/8 + 2/8 + 1/8 = 1/x
7/8 = 1/x
x = 8/7
So, working together, they take 1 hour 8.5 minutes approx

Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
Larry does 1/2 the job in 1 hr.
Willy does 1/4 job in 1 hr
David does 1/8 job in 1 hr.
Let x = time
1/2+1/4+1/8
=4/8+2/8+/8
=7/8 job in 1 hr
Just flip the equation to find out how long it takes.
8/7 hr = 1 1/7 hr = 1 hr 60/7 min = 1 hr 9 min (approx)
Ed