plague_sapiens, 1 year ago (edited 1 year ago)

Its easier:

10% of a 100: 100 * 0,1 = 10

2,5% of 33: 33 * 0,025 = 30 * 0,025 + 3 * 0,025 = 0,75 + 0,075 = 0,825

Thats how I calculate it mostly in my brain. But being smart I usually just type everything (like 9*9) in the calculator xD