User blog comment:Deshiba/Season 3 Armor and Armor Penetration/@comment-173.178.176.137-20121110165050

you forgot that armor reduction ALWAYS pass before amor % reduction ( mixing both is the worst decision u could make since you totally making your X% armor reduction if u have some TRUE armor reduction

Considarating this the new black cleaver is a pure fucking fail right at is creation (10 armor pen and % armor pen ) they putted it just to cheat us all since the 10 armor pen on it screw a part of the % making it a way lower then the # listed on the item

if u want to count take somebody starting with 31 armor pen (runes + 6 in mastery)

so 100- 36- 10 (from black cleaver) = 54 armor NOW u can remove the % so 46% from mastery and last wisper 54x 46%=24,84 (54-24,84= lets say 30)

so 30 armor on a 100 armor ratio its still 1/3 of the armor but far from the negative armor u calculated