Last month, you borrowed $100 from your friend. If you promise to pay her today, how much will you give to your friend if both of you agreed to return the money with a 10% increase?
The increase is $100 x 10/100 = $<<100*10/100=10>>10.
So you have to give $100 + $10 = $<<100+10=110>>110 to your friend today.
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