Talk:Master Yi/@comment-14052227-20130731161755/@comment-4605273-20130731171200

For basic attacks the following applies, and I don't think it's different in this case.

Infinity Edge is just used as an example. Crit damage is the same no matter the source. Ablities also scale the same way on Ability Power gained from items as well as runes.

The percentages add additvely to each other.

Lethality (10%) + Infinity Edge (50%) + Marks/Quints (33%) = 93% more crit damage = 293% total crit damage

For your other question. We're given a base scale here which is 60%. Lethality will ADD a given percentage of damage, which in this case is 10%. Following your way of putting it up mathematically, you probably want to have this instead:

0.6 + (0.1 * 0.6) = 0.66 = 66%

With the 93% increase this will be:

0.6 + (0.93 * 0.6) = 1.158 = 115.8%

This means the highest possible scale for a critting Alpha Strike (without wasting glyphs and seals) will be 165 + (215.8% AD).