Example:

Suppose, Suzane scored 65 out of 100 in previous exam. And this time, she scored 82 out of 100. Therefore:

New Value =  82
Old Value =  65

Improvement = New Value – Old Value = 82 – 65 =  17

Improvement % = (Improvement / Old Value) x 100 = (17 / 65) x 100 = 26.15 % 

Therefore, Improvement % of Suzane is 26.15%.