240% is the change from 15 to 51
Calculation steps:
[( 51 - 15 ) ÷ 15] x 100 = 240%
Formula
Percentage change = [(51 - 15) / 15] x 100
Subtract the new number by the original number
51 - 15 = 36
36 ÷ 15 = 2.4
2.4 x 100 = 240%
Example