Talk:Weapon Expertise (Season 2012 Mastery)/@comment-24.131.110.16-20111205155939/@comment-187.113.228.148-20111221075142

Easier explained, if you stack two different sources of 50% arpen, you will net a total of 75% pen, not 100%. You take away half of the enemy armor, and then take half again of whatever armor is left.

Just further information, the order which you apply the %pens doesn't matter, e.g. taking 40% and then 10% results in 46% total reduction, just like taking away 10% and then 40% results in 46% too.