SOLUTION: 15 workers can build a wall in12 days.How many workers are need if the wall is to be built in 9 days?

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Question 761591: 15 workers can build a wall in12 days.How many workers are need if the wall is to be built in 9 days?
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
One way to find how many is, what is the rate of work from 1 worker?
1 job is, "build the wall". From the given about 15 workers, 1 worker builds the wall in 12*15 days, so 1%2F%2812%2A15%29 jobs per day.

The rates of workers building together are simply added. How many workers, n, build the wall in 9 days? highlight%28+n%281%2F%2812%2A15%29%29%2A9=1%29. That is Rate*Time=Jobs.

n=1%2A%2812%2A15%29%2F9
n=%283%2A4%2A3%2A5%29%2F%283%2A3%29
highlight%28n=20%29 workers.