Question 1135888
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Here is yet another simple way to solve the problem.<br>
As tutor @ikleyn says after showing you three simple methods, you will be a better student if you know several ways of solving a problem.  The more tools you have in your tool bag, the more you will be able to accomplish.<br>
The hot water faucet fills the bathtub 4 times as fast as the cold water faucet.
That means in filling the tub together, the hot water faucet does 4/5 of the work.
Then, since the hot water faucet fills 4/5 of the tub in 3 minutes, the amount of time it would require to fill the tub alone is 5/4 of 3 minutes:<br>
{{{(5/4)*3 = 15/4}}} or 3 3/4 minutes, or 3 minutes 45 seconds