SOLUTION: A tap can fill a tank in 6 mins and another can fill the same tank in 8 mins .How long will it take to fill the tank if the two taps were opened at the same time?

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Question 1099571: A tap can fill a tank in 6 mins and another can fill the same tank in 8 mins .How long will it take to fill the tank if the two taps were opened at the same time?
Found 3 solutions by Theo, Fombitz, Edwin McCravy:
Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
rate * time = quantity

first tap fills the tank in 6 minutes.
rate for the first tap is 1/6 of the tank in 1 minute.

second tap fills the tank in 8 minutes.
rate for the second tap is 1/8 of the tank in 1 minute.

when they are both open, their rates are additive.

1/6 + 1/8 = 4/24 + 3/24 = 7/24

their combined rate is 7/24 of the tap in 1 minute when they are both open.

rate * time = quantity.

rate is 7/24 of the tank in 1 minute.
time is what you want to find
quantity is 1 full tank

formula becomes 7/24 * time = 1

solve for time to get time = 1 * 24/7 = 24/7 minutes = 3 and 3/7 minutes.


Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Rate x Time = Output
.
.
.
R%5B1%5D%2A6=1
R%5B1%5D=1%2F6
.
.
R%5B2%5D%2A8=1
R%7B2%5D=1%2F8
.
.
So when they're working together,
%28R%5B1%5D%2BR%5B2%5D%29t=1
%281%2F6%2B1%2F8%29t=1
t=1%2F%281%2F6%2B1%2F8%29
t=1%2F%288%2F48%2B6%2F48%29
t=1%2F%2814%2F48%29
t=1%2F%287%2F24%29
highlight%28t=24%2F7%29min

Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!
A tap can fill a tank in 6 mins
So the 1st tap's filling rate is matrix%281%2C2%2C1%2Ctank%29%2Fmatrix%281%2C2%2C6%2Cmin%29 or matrix%281%2C2%2C1%2F6%2Ctank%2Fmin%29

and another can fill the same tank in 8 mins .
So the 2nd tap's filling rate is matrix%281%2C2%2C1%2Ctank%29%2Fmatrix%281%2C2%2C8%2Cmin%29 or matrix%281%2C2%2C1%2F8%2Ctank%2Fmin%29

How long will it take to fill the tank if the two taps were opened at the same time?
Let the answer be x mins.

So together they can fill 1 tank in x minutes

So their combined filling rate is matrix%281%2C2%2C1%2Ctank%29%2Fmatrix%281%2C2%2Cx%2Cmin%29 or matrix%281%2C2%2C1%2Fx%2Ctank%2Fmin%29

Their combined filling rate must be equal to the sum of their 
filling rates:

matrix%281%2C2%2C1%2F6%2Ctank%2Fmin%29%22%22%2B%22%22matrix%281%2C2%2C1%2F8%2Ctank%2Fmin%29%22%22=%22%22matrix%281%2C2%2C1%2Fx%2Ctank%2Fmin%29

1%2F6%22%22%2B%22%221%2F8%22%22=%22%221%2Fx

Multiply through by the LCD of 24x

4x%22%22%2B%22%223x%22%22=%22%2224

7x%22%22=%22%2224

x%22%22=%22%2224%2F7

x%22%22=%22%223%263%2F7minutes

Edwin