A tank containing water started to leak. Did the tank

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A tank containing water started to leak. Did the tank contain more than 30 gallons of water when it started to leak? (Note: 1 gallon = 128 ounces)

(1) The water leaked from the tank at a constant rate of 6.4 ounces per minute.
(2) The tank became empty less than 12 hours after it started to leak.

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by [email protected] » Mon Jul 23, 2018 7:08 pm

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Hi All,

We're told that a tank containing water started to leak. We're asked if the tank contained MORE than 30 gallons of water when it started to leak. (Note: 1 gallon = 128 ounces). This is a YES/NO question. To start, the question can be rephrased as "did the tank contain MORE than (30)(128) = 3,840 ounces of water when it started to leak?"

1) The water leaked from the tank at a constant rate of 6.4 ounces per minute.

Fact 1 tells us the rate at which water leaks out of the tank, but we know nothing about how much water was actually in the tank to start.
Fact 1 is INSUFFICIENT

2) The tank became empty less than 12 hours after it started to leak.

Fact 2 tells us that it was less than 12 hours for the tank to completely empty, but we know nothing about how much water was actually in the tank to start.
Fact 2 is INSUFFICIENT

Combined, we know...
-The water leaked from the tank at a constant rate of 6.4 ounces per minute.
-The tank became empty less than 12 hours after it started to leak.

With this information, we can calculate the maximum amount of water that leaked out of the tank. At a rate of 6.4 ounces/minute, the tank would lose (6.4)(60) = 384 ounces of water per hour. At that rate, if the tank leaked for EXACTLY 12 hours, then it would have lost (12)(384) = 4,608 ounces of water. Since the tank leaked for LESS than 12 hours though, the amount of water lost was LESS than 4,608 ounces. The question asks whether the tank contained MORE than 3840 ounces of water. We don't know how much water the tank actually lost though - it could have been more than 3840 ounces, 3840 ounces exactly or less than 3840 ounces. Thus, the answer to the question is inconsistent.
Combined, INSUFFICIENT

Final Answer: E

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here is my approach to this problem in detail. Hopefully this will be helpful. Please do let me know if you feel an alternate approach would be better via a comment on the video.

The problem approach can be broken down into four steps:

1. Understanding that the Total Volume at the start = Volume remaining in the tank + Volume leaked.
2. Understanding that unless given we cannot assume a constant leak speed.
3. Converting to consistent units (either Gallon/hour or Oz/minute) is important and GMAT questions "usually" allow for easy calculations (as you will see when you do the conversion)
4. What does more than 30G entail in terms of time when a certain leak rate is given

Please see the video for complete reasoning and solution to this problem - Why is statement 2 insufficient? Should you convert to Gallons/hour or Ounce/minute. Why are statement 1 and 2 combined still insufficient? I have addressed these questions : https://www.youtube.com/watch?v=y-wkQw8OuNY&t=3s
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