100% is the change from 260 to 520
Calculation steps:
[( 520 - 260 ) ÷ 260] x 100 = 100%
Formula
Percentage change = [(520 - 260) / 260] x 100
Subtract the new number by the original number
520 - 260 = 260
260 ÷ 260 = 1
1 x 100 = 100%
Example