You can for example express 1/3 as 33.33333333333. But to round it to the nearest whole number it would just be 33%. For rounding if its 4 or under 4 like 10.4 you would round it to 10 same for 10.3, 10.2, 10.1. But for 5 and above you round up like 4.5 it would be 5 same goes for 4.6,4.7,4.8,4.9. Hope it helps! :D
