# SOLVED - How to calculate the probability of disease given a positive test from only true positive rate, false positive rate, and rate of disease?

Here's the problem I'm trying to solve:

"Calculate the probability of having the disease for a person with a positive test result."

The information I have is:

True positive percent = 90%

False positive percent = 1%

Percent of disease in general population = 0.01%

I'm getting confused because I'm used to working with counts and I'm not sure I can use the same formulas when I only have ratios. Hints are welcome!