80% is the change from 45 to 81
Calculation steps:
[( 81 - 45 ) ÷ 45] x 100 = 80%
Formula
Percentage change = [(81 - 45) / 45] x 100
Subtract the new number by the original number
81 - 45 = 36
36 ÷ 45 = 0.8
0.8 x 100 = 80%
Example