66.99% is the change from 521 to 870
Calculation steps:
[( 870 - 521 ) ÷ 521] x 100 = 66.99%
Formula
Percentage change = [(870 - 521) / 521] x 100
Subtract the new number by the original number
870 - 521 = 349
349 ÷ 521 = 0.6698656429942419
0.6698656429942419 x 100 = 66.99%