Question 1165522
<br>
You have received two responses showing perfectly good ways to solve a problem like this.<br>
There are many other ways; following is a solution by the method I find easiest to use.<br>
Given: 3 people to clean 1 pool in 4 hours.<br>
(1) The number of pools is increased from 1 to 6, a factor of 6.  Keeping the time the same, that means 6 times as many people.<br>
3*6 = 18<br>
(2) The amount of time is doubled, from 4 hours to 8 hours.  Keeping the number of pools the same, the number of people required is cut in half.<br>
18(1/2) = 9<br>
ANSWER: 9 people<br>