Question:
Two pipes A and B can fill a tank in 15 minutes and 20 minutes respectively. Both the pipes are opened together but after 4 minutes, pipe A is turned off. What is the total time required to fill the tank?
[A].
10 min. 20 sec. |
[B].
11 min. 45 sec. |
[C].
12 min. 30 sec. |
[D].
14 min. 40 sec. |
Answer: Option D
Explanation:
| Part filled in 4 minutes = 4 |
|
1 |
+ |
1 |
|
= |
7 |
. |
| 15 |
20 |
15 |
| Remaining part = |
|
1 – |
7 |
|
= |
8 |
. |
| 15 |
15 |
| Part filled by B in 1 minute = |
1 |
| 20 |
| x = |
|
8 |
x 1 x 20 |
|
= 10 |
2 |
min = 10 min. 40 sec. |
| 15 |
3 |
The tank will be full in (4 min. + 10 min. + 40 sec.) = 14 min. 40 sec.
