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?
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 2 of 4.
Savita said:
9 years ago
1/5 is taken wrt to 1 hr but not A B C they are taken as A, 2A, 4A which has to to be taken wrt 1hr but in equation how are they equating A, 2A,4A to 1/5 in an equation. if we want to solve an equation it should be write to 1 hr only.
YOGI M said:
9 years ago
[A + B + C] = 1/5.
According to question;
C = 2B = 4A----------- 2(2A )= 4A.
B = 2A.
[A] = ?
A + B + C = 1/5.
A + 2A + 4A = 1/5,
7A = 1/5,
A = 1/7 * 5,
A = 1/35 ==> 35hr.
According to question;
C = 2B = 4A----------- 2(2A )= 4A.
B = 2A.
[A] = ?
A + B + C = 1/5.
A + 2A + 4A = 1/5,
7A = 1/5,
A = 1/7 * 5,
A = 1/35 ==> 35hr.
(1)
Naveencool said:
9 years ago
Take A as x = 1, B = 2, C = 4.
The total is 7, each contribution is in 5 hours. Then 7 * 5 = 35 hours.
The total is 7, each contribution is in 5 hours. Then 7 * 5 = 35 hours.
(1)
Kishore said:
9 years ago
C is twice fast as B.
B is twice fast as A.
So, speed here If A = x, B = 2x, C = 4x.
Is speed increases time decrease. As we know from the above speeds we can get the value of time. B is twice fast as A. It mean just think speed multiplies. But time it should be divided.
So, If A takes x hour then B takes less time. It mean x/2. Similarly, C is twice fast as B. It mean if B takes x/2hr. Then C takes less than B as x/4.
So finally A takes x hr, B takes x/2 hr, and C takes x/4 hr.
B is twice fast as A.
So, speed here If A = x, B = 2x, C = 4x.
Is speed increases time decrease. As we know from the above speeds we can get the value of time. B is twice fast as A. It mean just think speed multiplies. But time it should be divided.
So, If A takes x hour then B takes less time. It mean x/2. Similarly, C is twice fast as B. It mean if B takes x/2hr. Then C takes less than B as x/4.
So finally A takes x hr, B takes x/2 hr, and C takes x/4 hr.
Naveen chowdary said:
9 years ago
Why not it is 1/x + 1/2x + 1/4x = 1/5?
Ramya said:
9 years ago
In some problem, they subtracted the values and here it is dividing. Can you please explain in detail?
Vikram kumar said:
9 years ago
ABC-A -B-C
5-35
7-1-2-4
Because 7 * 5 = 35 means that 1 * 35 = 35 answer, if we want to find B means 2 * 35 = 70h.
5-35
7-1-2-4
Because 7 * 5 = 35 means that 1 * 35 = 35 answer, if we want to find B means 2 * 35 = 70h.
Rahul said:
9 years ago
Given: B = 2 times of A.
C = 2 times of B.
Assume A = 1, so B= 2(A)= 2 and C= 2(B)= 4.
Total = 1 + 2 + 4 =7.
Now multiply it 7*5.
Answer = 35.
C = 2 times of B.
Assume A = 1, so B= 2(A)= 2 and C= 2(B)= 4.
Total = 1 + 2 + 4 =7.
Now multiply it 7*5.
Answer = 35.
Bappa said:
1 decade ago
Don't be confuse.
A x hours and B is twice fast it means is that B is faster than A.
So B is x /2. By this way B is twice faster than A.
A x hours and B is twice fast it means is that B is faster than A.
So B is x /2. By this way B is twice faster than A.
Laxmi said:
1 decade ago
Hi friends please tell how 1/5 is come here.
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