How is calculating 85% of $40.00 the same as calculating 40% of $85.00? how are the calculations different?

They are the same in that they both produce the same
.85(40) = 34
.40(85) = 34
A quick look at the factors of these two products reveals that we are essentially using the same numbers but switching the number that gets divided by 100 due to the percent. So we are two different problems yielding the same result.  

That's my take anyway :-)  Hope it helps