Aptitude - Pipes and Cistern - Discussion

Discussion Forum : Pipes and Cistern - General Questions (Q.No. 7)
7.
A tank is filled in 5 hours by three pipes A, B and C. The pipe C is twice as fast as B and B is twice as fast as A. How much time will pipe A alone take to fill the tank?
20 hours
25 hours
35 hours
Cannot be determined
None of these
Answer: Option
Explanation:

Suppose pipe A alone takes x hours to fill the tank.

Then, pipes B and C will take x and x hours respectively to fill the tank.
2 4

1 + 2 + 4 = 1
x x x 5

7 = 1
x 5

x = 35 hrs.

Discussion:
33 comments Page 4 of 4.

Laxmi said:   1 decade ago
Hi friends please tell how 1/5 is come here.

Aparna said:   1 decade ago
1/x+2/x+4/x = 7/x how is it possible?

Why don't we take x+2x+4X?

Can anyone explain me please?

Richa said:   1 decade ago
If B is half time as fast than A. Then B=2X?


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