A tank containing water started to leak. Did the tank contain more

Question

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.

ID: 700306

Bunuel · Accepted Answer

SOLUTION

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 --> 6.4 ounces per minute = 6.4*60 ounces per hour = 6.4*60/128 = 3 gallons per hour. We know the rate but not the size of the tank. Not sufficient.

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

(1)+(2) If the tank leaked water for a total of 11 hours, then the tank originally contained (time)(rate)=11*3=33 gallons of water, so more than 30 but if the tank leaked water for a total of 1 hour, then the tank originally contained (time)(rate)=1*3=3 gallons of water, so less than 30. Not sufficient.

Answer: E.

longhorn07 · Answer

(1 alone) Does not tell you anything about the size of the tank.  OUT

(2 alone) Does not tell you anything about the rate of leakage.  OUT

(1 & 2) Lets do some simple math to begin.

30 gallons = 3840 oz
6.4 oz/min = 384 oz/hr

Ah, nice! 3840 and 384 are easy numbers to work with. It should be pretty clear that...

10 hours to drain => 30 gallons
less than 10 hours to drain => less than 30 gallons
more than 10 hours to drain => more than 30 gallons

However, (2) does not help us out in this category, as the time could be either 1 or 11.  OUT

(1 or 2)  OUT

(Neither Sufficient)  CORRECT

gmatprav · Answer

E as well. 
1 is clearly not sufficient. 
2 Without knowing rate of leakage nothing can be said. - not sufficient.

1+2 at 6.4 ounce per min in 12 hours 36 gallons will be leaked so if tank leaks in 11:59 hrs tank must have > 30 gallons initially. This case yields "yes" answer. but if the tank is empty in 2 hours then tank has 6 gallons which is < 30. This case yields "no" answer. NOT SUFFICIENT.

mvictor · Answer

ok...30gallons * 128 = 1280x3 = 3840 ounces
the question is - did the tank contain more than 3840 ounces when it started to leak?

1. we know the rate of the leakage..but we do not know for how long it leaked..
2. tells that time is less than 12 hours..but we do not know the rate of the leakage..+ we do not know the exact time..

1+2.
6.4/min = 64*6=384 ounces/hour
if the tank leaked for > 10 hours, then it contained more than 30 gallons
if the tank leaked for less than 10 hours, then it contained fewer than 30 gallons.

since 2 alone tells that it is less than 12 hours..it can be either 11 or 9. 11-> over 30 gallons and 9-> less than 30 gallons.

E

grassmonkey · Answer

All the post above do a great job of answering the question, but I'll include my own approach in case anyone finds it helpful.

I find these problems hard because of (1) the inequalities and (2) the immediate decision that needs to be made about what numbers to convert. I'll try and illustrate how I triage these questions.

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.

Ok, at first glance I have a decision to be made about ounces vs. gallons. Without even doing anything else, I make the call that I'm going to convert 6.4 ounces to gallons because 6.4 oz/min is already a decimal, and making it a smaller decimal doesn't seem appealing. Therefore, convert the question (often an overlooked asset) to a ounces.

30 gallons = 30*(128) ounces = 3840 oz.

So the restated question is: Volume > 3840 oz. ?

At this point I can also see (as other posters have pointed out) that the answer is either C or E as neither statement is going to be sufficient on its own. Knowing that, I reach the second decision point: minutes vs hours?

I either convert the first statement into oz/hr or the second statement into minutes. Quickly eyeball your choices as either 6.4*60 or 12*60. In this case, it actually doesn't matter. Sometimes the numbers are easier going down one road, but here they look equally fine. I guess if pushed, it'd rather take advantage of 6.4*60 eliminating that decimal and take that one.

6.4*60 = 64*6 = 384 oz/hr

The tricky thing with statement 2 is that it's an inequality not a raw number. In order to remind myself of that, I actually include the inequality when I start combining stuff. It looks like this:

(384 oz/hr)*(<12 hrs) > 3840 oz ?

Now we can see the units will cancel we get a leaned down:

(384)*(<12) > 3840 ? --> remove the factor of 10 from the RHS
(384)*(<12) > (384)*(10) ? --> cancel common factors

We are then left with:

(<12) > 10 ?

Now this, although it might have seemed silly before, is very clear. Can the range of numbers less than 12 exceed 10? Yes of course it can (i.e. 11). Can it be less than 10? Yes of course (1, 2, 4, 7 etc).

Therefore, (E).

monikakumar · Answer

That was an awesome explanation

Basshead · Answer

Question:  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.

We have no idea what the size of the tank is. Insufficient.

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

We have no idea what the rate of the leak is. Insufficient.

(1+2) Statement 1 tell us that water leaked at a constant rate of 6.4 ounces per minute. Statement 2 tells us that the tank became empty  less than  12 hours after it started to leak.

Lets use extreme scenarios:

The tank became empty less than  1 second  after it started to leak. Did the tank contain more than 30 gallons? No.
The tank became empty less than  11.99 hours  after it started to leak. Did the tank contain more than 30 gallons? Yes

6.4 * 60 * 12 = 4600
30 * 128 = 3840

We can't conclude the tank contained more than 30 gallons. Insufficient.

Answer is E.

MHIKER · Answer

(1) 6.4 ounces  = \frac{1}{128}*6.4=0.05  gallon; No other information. Insufficient.

(2) Only time is given. Insufficient.

Using both information:

The maximum leakage can be less than  0.05*60*12=36  So there are several values less than 12 such as  5; 5*3=15  gallon. Insufficient.

The answer is  E.

CEdward · Answer

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)

30 gallons = 3840 ounces

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

6.4 ounces per minute = 384 ounces / hour

Insufficient b/c the rate has nothing to do with the volume in the container.

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

Insufficient b/c we have no idea what the rate of empty is.

C:

Suppose the tank took 10 and a little hours to empty.

10 x 384 = 3840 YES

1 hour?

1 x 384 = 384 ounces NO

E

Bambi2021 · Answer

6,4*5 = 32

32*4 = 128

1 gallon was emptied in 20 min

30 gallons would take 10 hrs

We dont know when it finished.

Answer: E

Posted from my mobile device

Hemant611 · Answer

In the explanation to combine 1&2, how did your get the rate as 3?

gmatbyexample · Answer

When you convert 6.4 ounces per minute to Gallons per hour, you will get the rate as 3 gallons per hour.

So basically 6.4 oz/min = 6.4*60/128 gallons / hour = 3 gallons / hour.

Does this help answer the question?

In questions like these it is always better to ensure that units are consistent throughout or we could get very different results.

I will post my solution to the problem shortly.

rvgmat12 · Answer

1.

1/20 gallon per minutes

Did it take 600 minutes or 10 hours for tank to be empty?
Not sufficient

2.

Tank was empty in less than 720 min
Not sufficient

1&2.

Not sufficient

E

gmatbyexample · Answer

Sorry for the delay, 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

I have tried to answer questions like - which units to convert to - Gallons/hour or Ounce per minute. Even when you combine statements 1 and 2, why is the information not sufficient? How do I translate "more than 30 gallons" into something mathematical to work with.

Please subscribe to my channel for more: https://bit.ly/GMATExample_U

Vegita · Answer

Bunuel

Should we generally try to work with higher units in this case hours and gallons instead of the smaller units units to save time?

Will doing this save us from more calculations in questions involving many units?

sacharya · Answer

V>3840 ounces ?

Not Sufficient

Not sufficient

Not Sufficient

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GMATking94 · Answer

Good question.

We need to determine weather the tank contained more than 30 gallons of water.??

S1: The water was leaking at a constant rate of 6.4 ounces per minuite. Not sufficient.
S2: The tank emptied in less than 12 hours. Not sufficient.

Combining S1 & S2.
The leak rate was 6.4 ounces per minuite and let's assume it took 12 hours. We get that the tank in this case contained 36 gallons of water. But we are told it took less than 12 hours and in that case we do not have a definite answer to our question. It can be <> 30 gallons..

Hence, (E) is our answer.

Rhaenyra · Answer

Question asks: Is amount of water in tank (let it be Q) < 30 gallons?
In oz, that is: Is Q < 30 x 128? I.e. is Q < 3840?
 
(I) rate of leakage =6.4 oz per minute
Q = rate x time = 6.4 x time 
We need to find if 6.4 x time < 3840? Or is time < 3840/6.4 minutes?

That boils down to : Is time < 600 minutes? We don/t know that. Insufficient.

(II) tells us Time < 12 hours or Time < 720 minutes. Don't know rate here, Insufficient.

(I) + (II)
(I) asks us if Time < 600? (II) tells us that Time < 720. That's not enough to tell if Time < 600. Time could be 500 or 700 mintes. Insufficient.

Hence, answer is E.

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A tank containing water started to leak. Did the tank contain more

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