Using the binomial theorem you can solve ball urn problems. Like say for example a urn has 4 green balls and 3 white balls. You draw two balls. What's the probability you draw 2 white balls? I just made this problem up off the top of my head. But anyways using the binomial theorem (7C2)(3/7)^2*(4/7)^5 However this is wrong correct? Because it's impossible to draw two balls simultaneously... I just realized that. So how do you solve this problem then?