See I love quick and dirty rules to get close enough through estimation for whatever I'm mental mathing, because if I need exact numbers I'm turning to a computation device

20% of 36.23 I'd be going "okay 20% of 10 is 2, 3 10s in 36 so 3x2=6, and 6.23 is pretty close to half 10 and half 2 (from my previous 20% of 10 calculation) is 1 so 20% of 36.23 is slightly more than 7"

36.23% of 20 I'd be going "30% of 10 is 3, 2 10s in 20 so 2x3=6, 6.23% is close to 5 so half of 3 is 1.5, 6+1.5=7.5 so 36.23% of 20 is a bit more than 7.5"

Now which is closer to correct? Ehh I'm not sure I haven't used a calculator yet, but I'm mental mathing so chances are my estimation got me close enough that I can just round to whichever direction is safer for errors and call it good. Usually I'm mental mathing to figure out splitting a bill, a tip or to double check some machine computed math that looks wrong, and none of those call for perfect precision, just getting close enough that it doesn't matter