Answer:
18 hours
Explanation:
By the 6 water pumps working together to fill a tank, we can assume that they are all contributing an equal amount. They are all contributing 1/6th of the total effort.
We can split the initial 15 hours into a separate portion for each pump. 15 doesn't go evenly into 6, so I will convert hours to minutes (for my own ease)
15 hours = (15 x 60) = 900 minutes
Now, 900 is divisible by 6:
900 / 6 = 150
So, to fill the tank (because the pumps will be flowing at the same rate), we need 150 minutes of work from each.
If we were to divide 900 minutes among 5 pumps, each pump would need to contribute 180 minutes (900 / 5).
180 is 120% percent of 150, so the total time is 120% more.
900 minutes (15 hours) , 120% of 900 = 1080 minutes (18 hours)
So, the overall time would be 18 hours.
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another way I found this answer!
theoretically...
If they were to work individually, it would take a single tank 900 · 6 minutes.
So, it would take 1 sing 5400 minutes.
If there were two sinks, 5400 minutes would be divided into two halves, and the total time would be cut in half.
So (5400 / 2) the total time would be 2700 minutes
If there were three sinks, 5400 would be divided by 3, and the total time would be (5400 / 3) 1800 minutes.
If there were four sinks, 5400 would be divided by 4, and the total time would be (5400 / 4) 1350 minutes
And, if there were five sinks, 5400 would be divided by 5, and the total time would be (5400 / 5) 1080 minutes.
{1080 minutes = 18 hours}
To check- when there are 6 sinks, 5400 is divided by 6 (5400 / 6), and it would take 900 minutes.