The Brainliest Answer!
That's simple 40/100 = 0.4 
Hope it helped. ^_^
2 5 2
ok. well according to my information the probability is always between 0 and 1, and the percentage range is 0% to 100%, right?
now, take a look between those 0 to 1 and 0% to 100% they have a difference of 100[multiplied or divided] now multiply 100 with any probebility, it will give you the percentage number of it. 
[not sure, because I'm answering this according to what I've studied [till std.10th] 
tell me if you still didn't understand, then I may give example of it.... ^_^