Two pipes, A and B, empty into a reservoir. Pipe A can fill the

Question

Two pipes, A and B, empty into a reservoir. Pipe A can fill the reservoir in 30 minutes by itself. How long will it take for pipe A and pipe B together to fill up the reservoir?

(1) By itself, pipe B can fill the reservoir in 20 minutes.
(2) Pipe B has a larger cross-sectional area than pipe A.

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ManifestDreamMBA · Answer

Time taken by A = 30mins
To calculate Time taken by A and B, we need time taken by B = ?

S1
B = 20
Time taken together = 20*30/50
Sufficient

S2
Pipe B has a larger cross-sectional area than pipe A
We still don't know time taken by B to fill up the reservoir
Insufficient

Answer A

Dereno · Answer

Two pipes A and B fill a reservoir. We need to find the time taken by both pipes working together.

Given time taken by Pipe A = 30 mins.

Statement 1:

(1) By itself, pipe B can fill the reservoir in 20 minutes.

Since time of B is given, it’s sufficient along with Time of pipe A to find the total time taken by A and B together.

Ta : Tb = 30:20

efficiency ratio Ea : Eb = 2:3

total capacity of reservoir = LCM (20,30) = 60.

total time of A and B together = 60/(2+3) = 12 mins.

Option A is sufficient. Eliminate option B, C and E.

Statement 2:

(2) Pipe B has a larger cross-sectional area than pipe A.

Larger cross sectional area of pipe B > pipe A.

But, how much larger ?

Hence,  Not Sufficient

Option A

Ayeka · Answer

Two pipes, A and B, empty into a reservoir. Pipe A can fill the reservoir in 30 minutes by itself. How long will it take for pipe A and pipe B together to fill up the reservoir?
Time taken by A= 30 mins 
Time taken by A+B=?

(1) By itself, pipe B can fill the reservoir in 20 minutes.
Time taken by B= 20 mins 
Time taken by A+B = 1/((1/30)+(1/20))= 1/(50/600)= 60/5= 12
Sufficient

(2) Pipe B has a larger cross-sectional area than pipe A.
Insufficient

Answer: A

akshatj28 · Answer

To determine how long it will take for pipe A and pipe B together to fill the reservoir, we need to find the rate at which pipe B fills the reservoir. We are given that pipe A fills the reservoir in 30 minutes, so its rate is 1/30 of the reservoir per minute.

Statement (1): By itself, pipe B can fill the reservoir in 20 minutes.

If pipe B fills the reservoir in 20 minutes, its rate is 1/20 of the reservoir per minute.
 Together, their combined rate is 1/30+1/20.
 To add these fractions, we find a common denominator, which is 60: 2/60+3/60=5/60=1/12 of the reservoir per minute.
 Therefore, the time it takes for both pipes together to fill the reservoir is the reciprocal of their combined rate, which is 1/(12)=12 minutes.
 
Since we can find a specific time, Statement (1) ALONE is sufficient.

Statement (2): Pipe B has a larger cross-sectional area than pipe A.

The rate at which a pipe fills a reservoir depends on its cross-sectional area AND the velocity (speed) of the water flowing through it (Rate = Area × Velocity).
 While pipe B has a larger area, we don't know the velocity of the water in pipe B compared to pipe A.
 If the water velocity in B is the same or higher than in A, pipe B will fill faster than if its area was the same as A.
 However, if the water velocity in B is significantly lower than in A, pipe B could fill slower, the same, or faster than A, but we cannot determine its exact rate.
 For example, if pipe B's area is twice that of A, but its water velocity is half that of A, its filling rate would be the same as A (2×Area×0.5×Velocity=Area×Velocity). If its velocity were the same as A, its rate would be double.
 
Since we cannot determine a specific filling rate for pipe B, we cannot find a unique time for both pipes together.
 Therefore, Statement (2) ALONE is not sufficient.

Conclusion: 
 Statement (1) ALONE is sufficient to answer the question, but statement (2) ALONE is not sufficient.

The correct answer is A.

Two pipes, A and B, empty into a reservoir. Pipe A can fill the

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GMAT Data Sufficiency (DS) Questions

Two pipes, A and B, empty into a reservoir. Pipe A can fill the

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