Its a story problem.....
A homeowner estimates that it will take 8 days for her to paint her house. A professional painter estimates that he could paint the house in 5 days. How long will it take if they work together?
I got 6.5 but it was wrong... AHHH HELP!
Barkley Hound
Favorite Answer
It is not the average. Let's say you take 8 days and he also takes 8 days. You would finish in 1/2 the time. Not the average.
Since the professional can do it in 5 days the answer must be less than 5 since you are helping.
Let's say there are A units of work to be done. If you do it yourself the speed is A/8 per day.
The professional can do it A/5 per day. Both together would be A/8+A/5 per day.
Since the total is A the total days is A/(A/8+A/5) = 40/13 or 3.077 days. The A cancels out in the formula.
A/(A/8+A/5) = A/(5A/40+8A/40) = A/(13A/40) = 40A/13A = 40/13
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