Milk flows into a vat at a constant rate through a metal pipe.

Question

Milk flows into a vat at a constant rate through a metal pipe. At the same time, milk is pumped out of the vat at a constant rate through another metal pipe. At what rate, in liters per minute, is the amount of milk in the vat decreasing?

(1) The amount of milk initially in the vat was 100 liters.

(2) Milk flows into the vat at a rate of 5 gallons every 5 minutes and out of the vat at a rate of 5 gallons per minute.

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GMATinsight · Answer

Question: Net rate = Out rate - Incoming Rate = ?

Statement 1  : Initial amount = 100
 Not sufficient

Statement 2  : Milk flows into the vat at a rate of 5 gallons every 5 minutes and out of the vat at a rate of 5 gallons per minute.
Incoming rate = 1 gallon per minutes
Out rate = 5 gallons per minute
Net rate = 5-1 = 4 gallons per minute

SUFFICIENT

Answer: Option B

Related Video: 
  https://www.youtube.com/watch?v=i6NiIG35pzo

ManifestDreamMBA · Answer

At what rate, in  liters per minute , is the amount of milk in the vat decreasing?
Let rate of inflow be x and outflow be y

Statement
Volume = 100L
Insufficient, doesn't tell anything about speed

Statement2
x=5G/5m = 1G/m
y=5G/m
Difference = 4G/m
1G = 3.78541 L
Rate = 4*3.78541 L/m ~ 14L/m
 Answer B if we are expected to know 1G=3.78541L, else answer is E

Dereno · Answer

Milk flows in and milk is pumped out at a different constant rates. The rate of milk decreasing is ?

Statement 1:

(1) The amount of milk initially in the vat was 100 liters.

Initial capacity alone is not sufficient to answer. Hence,  Insufficient

Statement 2:

(2) Milk flows into the vat at a rate of 5 gallons every 5 minutes and out of the vat at a rate of 5 gallons per minute.

Inflow = 5 gallons/ 5 min = 1 gallon per minute.

Outflow = -5 gallons / minute.

rate of decreasing = -5+1 = -4 gallons / minute.

Water is decreasing at the rate of 4 gallons per minute, irrespective of the capacity of the tank.

Hence,  Sufficient

Option B

Abhiswarup · Answer

question needs to find the rate at which amount of milk is decreasing.

(1) The amount of milk initially in the vat was 100 liters.
Insufficient as no information comes out from at what rate milk is going in Vat & at what rate milk is taken out from VAT.

(2) Milk flows into the vat at a rate of 5 gallons every 5 minutes and out of the vat at a rate of 5 gallons per minute.
Basically it provides for both incoming & outgoing rate of milk from Vat. Statement is sufficient
The rate is 1/gallon/min- 5gallons/min= -4 gallons/min
Answer is B.

ankitksingh · Answer

Hi, The question seems to have some ambiguity, based on data the answer could be  E  or  C

Why E?
The question is asking the rate in liter per minute, where as the options have unit in Gallon which takes an underlying assumption that the person knows Gallon to liter conversion which is not given and is some extra info.

Why C?(The most accurate answer in my opinion)
Lets assume the person knows the conversion, there would be 2 case where the rate of flow would change.

Case1:   When there is some milk is in the vat

Milk_in = 5gal per 5min = 1gal/min
Milk_out = 5gal/min

rate of decrease = 5-1 =  4 gal/min

Case2: When there is no milk is in the vat

Here, the flow in would be the limiting factor. So once we have exhausted the 100L initial reserved milk(since the outflow is faster than inflow), the flow would immediately drop to  0 gal/min(refer to below calculation)

Milk_in = 5gal per 5min = 1gal/min
Milk_out = 1gal/min

rate of decrease = 1-1 =  0 gal/min

Hence there would be 2 rate of decrease, 
 when there is some liquid then 4gal/min, when all the initial liquid is depleted than 0gal/min

Milk flows into a vat at a constant rate through a metal pipe.

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GMAT Data Sufficiency (DS) Questions

Milk flows into a vat at a constant rate through a metal pipe.

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards