SOLUTION: A tank can be filled by two pipes separately in 10 and 15 minutes respectively. When a third pipe is used simultaneously with the first two pipes, the tank can be filled in 4 minut

Question 150822: A tank can be filled by two pipes separately in 10 and 15 minutes respectively. When a third pipe is used simultaneously with the first two pipes, the tank can be filled in 4 minutes. How long would it take the third pipe alone to fill the tank?
Found 2 solutions by mangopeeler07, ankor@dixie-net.com:
Answer by mangopeeler07(462) (Show Source): You can put this solution on YOUR website!
A tank can be filled by two pipes separately in 10 and 15 minutes respectively. When a third pipe is used simultaneously with the first two pipes, the tank can be filled in 4 minutes. How long would it take the third pipe alone to fill the tank?

find the rate it would take the first two pipes together.

1/10+1/15=x
25/150=x

25/150y=1
y=150/25
y=6

6 minutes for Pipe A and B together.

1/6+z=1/4

Subtract 1/6 from both sides
z=1/12

So the third pipe can fill the tank in 12 minutes.
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
A tank can be filled by two pipes separately in 10 and 15 minutes respectively. When a third pipe is used simultaneously with the first two pipes, the tank can be filled in 4 minutes. How long would it take the third pipe alone to fill the tank?
:
Let x = time (in min) required by the 3rd pipe alone:
Let the full tank = 1
:
+ + = 1
:
Multiply equation by 30x to eliminate the denominators, results
3x(4) + 2x(4) + 30(4) = 30x
:
12x + 8x + 120 = 30x
:
20x + 120 = 30x
:
120 = 30x - 20x
:
120 = 10x
x =
x = 12 min for the third pipe to fill it alone
;
:
Check solution using a calc
(4/10) + (4/15) + (4/12) =
.4 + .267 + .333 = 1

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