Talk:Riven Mods/@comment-51.7.242.67-20190619211540/@comment-4448946-20190709153411

Yeah, the probability of that happening is nowhere near as low as you think it is. So here's the math the the chance of at least 2 out of 5 rifle rivens sharing the same weapon.

There are only 63 different weapons a rifle riven can be for. As you unlock them the chances of each of them not matching any of the previous rivens are 63/63, 62/63, 61/63, 60/63, and 59/63. For the probability of  oa setf events all happening you multiple the probabilities together so...

(63/63)*(62/63)*(61/63)*(60/63)*(59/63)= ~0.85

That means there's an 85% chance that none of the rivens will be for the same weapon, but it also means there's a 15% chance they will be. So, approximately 1 in 7 people will recieve 2 rivens for the same weapon out of 5 primary rivens.

With a probability of 1 in 7 your situation will be happening all the time.