Mastering the Math of Filling and Draining Tanks

A tank with a volume of 500 gallons can be filled by one pipe in 25 minutes and drained by another pipe in 50 minutes. How long will it take to fill the tank if both pipes are open?

• A. 50 minutes
• B. 52 minutes
• C. 55 minutes
• D. 56 minutes

Answer: (A)

To determine how long it will take to fill the tank when both pipes are open, we should first ascertain the filling and draining rates of the respective pipes. The filling pipe can fill the tank in 25 minutes. This means it can fill 1/25 of the tank's volume per minute. Conversely, the draining pipe empties the tank in 50 minutes, equating to a rate of 1/50 of the tank's volume per minute. When both pipes are open simultaneously, the net rate of filling the tank is derived by subtracting the draining rate from the filling rate. Hence, we have: Filling rate: 1/25 tanks per minute Draining rate: 1/50 tanks per minute To combine these rates effectively, we find a common denominator. For 25 and 50, the lowest common multiple is 50: - The filling rate becomes 2/50 tanks per minute (since 1/25 = 2/50). - The draining rate remains 1/50 tanks per minute. Now, we can subtract the draining rate from the filling rate: Net Rate = (2/50) - (1/50) = 1/50 tanks per minute. Therefore,

When preparing for the Officer Aptitude Rating (OAR) test, a question about filling and draining a tank can pop up out of nowhere. It might feel like a nuisance, but with the right approach, you can make short work of it. So, you’ve got a tank that holds 500 gallons. One pipe fills it in 25 minutes, while another pipe empties it in 50 minutes. How long to fill the tank when both pipes are open? Let’s break it down together!

First off, let’s figure out the filling and draining rates of the pipes. Remember, this isn’t rocket science—just good ol’ math!

• Filling Pipe: If it fills the tank in 25 minutes, it’s filling at a speed of ( \frac{1}{25} ) of the tank's volume each minute.

• Draining Pipe: This one empties the tank in 50 minutes, which means it drains at ( \frac{1}{50} ) of the tank's volume each minute.

You see where we’re going with this? When both pipes are active, the net filling rate can be found by subtracting the draining rate from the filling rate. So, let’s combine these rates to see how long it’ll take!

To do this, we need a common denominator, and guess what? For our primes 25 and 50, it’s 50. Here’s how it breaks down:

• The filling rate converts to ( \frac{2}{50} ) tanks per minute (because ( \frac{1}{25} = \frac{2}{50} )).

• The draining rate stays as ( \frac{1}{50} ) tanks per minute.

Now, we simply subtract. So the net rate works out like this:

• Net Rate = ( \frac{2}{50} - \frac{1}{50} = \frac{1}{50} ) tanks per minute.

Since we’re filling at a rate of ( \frac{1}{50} ) of the tank every minute, it means we can fill the entire tank in 50 minutes! There you have it—an answer that not only makes sense but also feels like a little victory, doesn’t it?

So, looking back, we’ve untangled this math problem step by step, a bit like navigating the maze of questions on the OAR test. Each type of question may seem overwhelming at first, but with practice and a clear understanding, you can tackle them all. If math can feel like a heavy weight on your shoulders, remember that the more you engage with it, the lighter it gets. And hey, once you've wrapped your head around this one, you can take it to the next level—practice makes perfect!

As you gear up for your OAR preparation, keep these strategies handy. Who knows? You might just transform dreaded math problems into your favorite brain teasers! With the right mindset and tools, you’re equipped to conquer any challenge that comes your way. And always remember, whether you’re filling tanks or solving test questions, you’ve got the power to figure it all out!