Answer: 21.875 gallons
To Know:
Keep in mind a percent divided by 100 becomes a decimal.
There are two ways to solve this problem.
The first is to find how much water is in the fish tank already:
We can set up a proportion to solve. This proportion has units of percentage on the top and gallons on the bottom.
It will help us to find how much water is in the fish tank:
1x = 3.125
x = 3.125
Now we can solve for how much water is needed to fill the tank:
25 - 3.125 = 21.875 gallons
The second is to find how much is needed using the percentages:
100% - 12.5% = 87.5%
Now to find how much is needed:
25 * 0.875 = 21.875 gallons
Have a nice day!
I hope this is what you are looking for, but if not - comment! I will edit and update my answer accordingly.
- Heather