Question

Why does a 65% decrease followed by a 66% increase does not lead back to the starting value

Answer 1

We will understand this by an example

Take a number say 100

Now 65% decrease in 100 would be 100 - 65% of 100 = 35

and 66% increase in 35 will be 35 + 66% of 35 = 57.1

See the difference

In first case we are decreasing 65% of 100 from 100

In second case we have 35 not 100

So increasing 66% of 35 in 35 would certainly be different from decreasing 65% of 100 from 100