Question 446383
<br>
Here is an alternative to the standard algebraic method shown by the other tutor.  This method works especially well in this particular problem because the numbers are "nice".<br>
The three times for the three people to fill the pool, in minutes, are 30, 45, and 90.<br>
Consider the least common multiple of those times, which is 90 minutes.  In 90 minutes, ...
Jill could fill the pool 90/30 = 3 times;
Jack could fill the pool 90/45 = 2 times; and
John could fill the pools 90/90 = 1 time<br>
Therefore, in 90 minutes, the three of them could fill the pool 3+2+1 = 6 times.<br>
And if they can fill the pool 6 times in 90 minutes, the time it takes them to fill the pool once is 90/6 = 15 minutes.<br>
ANSWER: 15 minutes<br>