Guild Wars 2

“Sigils that have a chance to trigger on critical hits stack their chance percentages multiplicatively, not additively. For example, two major Sigils of Fire, which each have a 20% chance to trigger on critical hit, will have a 36% chance to trigger, not 40%.”

I know I rusty on my math but I do not understand how two 20% sigils get to 36%. How do you get to that number?

Thanks

Chance sigil 1 crits = 20%
chance it does not crit = 80%

Chance sigil 2 crits = 80% (chance the 1st did not crit) * 20% = 16%

Then chance sigil1 crits (20%) + chance sigil2 crits (16%) = 36%

Hope that made sense

Ah yes thank you very much