How can we calculate renth?

Question

I want to make a little machine that counts renth. but i dont know how to make it. pls help md with this:
i have a certain amount of money, i have a percentage of renth and i want to add that percentage to the money

Answer 1

#instanciate money and percentage
money = 100
percentage = 0.10
#compute rent
rent = money*percentage
#add rent
money += rent

or if you want it fast:
money += money*percentage

Answer 2

thx