1. The problem statement, all variables and given/known data Calculate the probability that the electron in the ground state of a hydrogen atom is in the region 0 < r < 3.75a0. 2. Relevant equations a0=.0529 nm P(r)=4(Z/a0)^3*r^2*e^(-2Zr/a0) 3. The attempt at a solution I am confused because I am not sure if I am supposed to use 3.75a0 as my radius. I guess I am not supposed to since I did that and got it wrong. I cannot figure out what else to do. However, I have also seen the probability density written as: P(r)[tex]\Delta[/tex]r=[4(Z/a0)^3*r^2*e^(-2Zr/a0)][tex]\Delta[/tex]r If this is the correct formula, I am not sure what to use for delta r. Any help would be much appreciated.