Fish tank word problem. Help!

[udcide]

I need explanation of how answer was figured out as well as the answer. I figured out the others I had to do but this one is stumping me.


Question

Mark's fish tank was filled half way. He added 9 gallons of water to the tank and found that it was then 7/8 full. How much water can the tank hold altogether?

Thank You

[udcide]

I guess no one is really on here to help

[Subhotosh Khan]

I need explanation of how answer was figured out as well as the answer. I figured out the others I had to do but this one is stumping me.


Question

Mark's fish tank was filled half way. He added 9 gallons of water to the tank and found that it was then 7/8 full. How much water can the tank hold altogether?

Thank You

We help when we see that you have done some work - and need a push. You did not show any work - so nobody helped.

Hint:

7/8 - 1/2 = 3/8 ≡ 9

Please share your work with us, indicating exactly where you are stuck - so that we may know where to begin to help you.

[udcide]

ok TY

let me see if I am understanding somewhat or correct

9 gallons is 3/8?
18 gallons would be 3/4?
or am I better off saying
12 + 9 = 21 and 7/8x would make answer 24?
half would have been 21 right?

Am I atleast on the right track of getting my explanation or even answer correct?

[Subhotosh Khan]

if the volume of the tank is V gallons, then:

1/2 * V + 9 = 7/8 * V

7/8 * V - 1/2 * V = 9

3/8 * V = 9

V = 9 * 8/3 = 24 gallons

[udcide]

TY so much

So I guess my answer was correct and atleast I was on track with my explanation. My problem is that I tend to second guess myself even when I might be correct.

[Denis]

So I guess my answer was correct and at least I was on track with my explanation.
My problem is that I tend to second guess myself even when I might be correct.
Well, in most cases, you can check yourself if you're correct by substituting your
answer back in the problem; in this case:
if 24, then half is 12; add 9, so 21 : 21/24 = 7/8 ; get my drift?

[burakaltr]

I need explanation of how answer was figured out as well as the answer. I figured out the others I had to do but this one is stumping me.


Question

Mark's fish tank was filled half way. He added 9 gallons of water to the tank and found that it was then 7/8 full. How much water can the tank hold altogether?

Thank You

8x=tank volume

4x+9=7x

so what is 8x?