How do you turn a percent into a decimal?
Divide by 100, so
Actually the word 'percent' means 'per 100' (maybe you recognize 'cent' as '100 in a dollar/euro/whatever').
So % is just short for "/100"
You might as well write
To turn a fraction into a percentage, you just do the reverse:
Multiply by 100, effectively doing
It's really that easy!