SOLUTION: A painter can paint a building in 15 days and a coworker can do the same job in 10 days. If the first painter starts and 3 days later the coworker joins in to help finish the job,
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Question 1108519: A painter can paint a building in 15 days and a coworker can do the same job in 10 days. If the first painter starts and 3 days later the coworker joins in to help finish the job, how many days does it take to paint the building? Found 3 solutions by josgarithmetic, josmiceli, ikleyn:Answer by josgarithmetic(39618) (Show Source):
You can put this solution on YOUR website! What fraction of the job does 1st painter
get done in 3 days?
His rate of painting is [ 1 building ] / [ 15 days ]
That means there is of the building
left to paint
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Add their rates of painting to get their rate
painting together
Let = their time in days to paint
of the building working together
Multiply both sides by
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Add the 3days to 4.8 days
It takes 7.8 days to paint the building
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check the math & get a 2nd opinion if needed
The first painter makes of the job per day; it is his rate of work.
In three days he did = of the job; hence, of the job remained.
The second painter makes of the job per day; it is his rate of work.
Hence, their combined rate of work is + = + = = of the job per day.
Hence, it will take = = = of the day for the two painters to complete the painting.
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So, my answer coincides with that by @jomiceli.
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It is a typical joint work problem.
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