where do i start? i'm frustrated

[kristen1995]

A 2000L tank containg 550L of water is being filled with water at the rate of 75 L per minute from a full 1600 L tank.How long will it be before the two tanks have the same amount of water? :? Thanks :?

 

[Deleted member 4993]

A 2000L tank containg 550L of water is being filled with water at the rate of 75 L per minute from a full 1600 L tank.How long will it be before the two tanks have the same amount of water? :? Thanks :?

You need find the time elapsed.

So define your unknown(variable)

Let the time at which both of the tanks have equal volume = t minute

after t hours - how much water in the 2000 L tank = 550 + t*75

after t hours - how much water in the 1600 L tank = ???

Since those two volumes are equal - equate those and find 't'

 

[kristen1995]

Thank you. How I fiqured this problem out is:

t +1600= 550 + 75t
-t -t

1600= 550 + 75t
I subtract 550 from both sides and 1600 becomes 1050. Then I divide by 75t and get 14 minutes. Is that how you do it? Algerbra is so confusing sometimes. :?

 

[Denis]

No. If it was 1050:
1600 - 1050 = 550
550 + 1050 = 1600
Try again.
And check your answer(s) as I showed above.
Hint:
There is 550 + 1600 to start with, right? So total of 2150.
So 2150/2 = 1075 must end up in each container: kapish?

 

[kristen1995]

Thanks for the hint Denis.I'm still :?

 

[Deleted member 4993]

Thank you. How I fiqured this problem out is:

t +1600= 550 + 75t <<< That is not correct - how did you get that? From tank 2 - we are getting water out - so it must be going down with increase of time. You have to subtract "75t" from the original volume of 1600

so your equations would become:

after t hours - how much water in the 2000 L tank = 550 + t*75

after t hours - how much water in the 1600 L tank = 1600 - t*75

Now equate and solve.

Denis gave you another way to solve it - both method will give you the same answer.


-t -t

1600= 550 + 75t
I subtract 550 from both sides and 1600 becomes 1050. Then I divide by 75t and get 14 minutes. Is that how you do it? Algerbra is so confusing sometimes. :?

 

[Denis]

You seem confused with the t*75...

1600 - 525 = 1075
550 + 525 = 1075

So you know that 525 L is required amount.
Since speed is 75 L per min, then time = 525/75 = 7 minutes.
Got that?

Now try to see why using 75t comes out the same...