1st Method; the value 1% of 2500 is 1% x 2500 = 0.01 x 2500 = 25
This is a decrease, then it's - 25
2nd Method:
The 2500 represents 100%. If we have to decrease it by 1%, then the remainder value in % will be 100% - 1% = 99%. The value of 99% is:
2500 x 99% = 2500 x 0.99 = 2475
From 2500 it becomes 2475 after the decrease of 1%. Inn value the decrease is 2500 - 2475 = 25