Question 1197896
<br>
For a quick informal solution, if a formal algebraic solution is not required....<br>
The smaller hose takes twice as long as the larger to fill the pool alone; that means it works half as fast.
So when the two hoses together fill the pool in 20 minutes, the smaller hose is doing 1/3 of the job and the larger hose is doing 2/3 of the job.
So the smaller hose fills 1/3 of the pool in 20 minutes; that means it would take it 3*20 = 60 minutes to fill the whole tub alone.<br>
ANSWER: 60 minutes<br>
NOTE: Even if a formal algebraic solution is needed, you can get good mental exercise by solving the problem in a manner similar to the above, using logical reasoning and simple arithmetic.<br>