Question 1206761
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Both of the responses from other tutors show basically the same good method for solving the problem.<br>
Here is a different method for working problems like this that I personally like.<br>
We are given that it takes 10 days for a certain given amount of work to get done, and we are asked how many days it would take with different parameters.  We can find the answer by multiplying the given figure of 10 days by ratios representing the change in each parameter.<br>
(1) 16 pumps instead of 18; fewer pumps means more time; multiply by 18/16 = 9/8.
(2) 1736 tonnes of water instead of 2170; fewer tonnes means less time; multiply by 1736/2170 = 4/5.
(3) working 9 hours a day instead of 7; more hours per day means fewer days; multiply by 7/9.<br>
{{{(10)(9/8)(4/5)(7/9)=7}}}<br>
ANSWER: 7 days<br>