Thread: WordProblem with percentages

If the water level of a pool dropped by 20% over night, by how much percent does it need to increase to get to the same level? Answer is 25%
I set it up like this x-x80/100=y
y+y(z/100)=x i dont know how to quantify a percentage differently and thats where i think I'm wrong..scratch that i know I'm wrong cause i have 2 equations with 3 variables. Can i get a hint? Don't want the full set up, i want to get it, cause ill feel stupid if i dont.

Try this equation (letting x be the original level of the water and y be the amount by which you increase the reduced level to get the original level):





The x's cancel out, and we have y=1/.8=5/4=1.25

When we multiply by 1.25, we are increasing the value by 25%.