Easy to do:

for 50% it

1*0.50 = 50%
1*0.50*0.50 = 25%
1*0.50*0.50*0.50=12.5%
1*0.50*0.50*0.50*0.50=6.25%
1*0.50*0.50*0.50*0.50*0.50=3.125%

Hope that explains it.