there is no good answer to this, but roughly 3.6. the best explanation is to find two numbers that multiply to itself to get close to 13. in this case, 3*3 will get us the closest in terms of whole number, so keep going. 3.5^2 is 12.25, so we are getting closer. 3.6^2 is 12.96. at that point, you would get smaller and smaller to a repeating number, so 3.605 is the closest really you can get
