Question

A friend lends you $260, which you agree to repay with 3% interest.How much will you have to repay?How much of that was interest?

Answer 1

To answer this question we will use the following formula to compute the x% of y:

$y\times\frac{x}{100}.$

Since you have to repay with 3% interest, then you have to pay 103% of the original amount.

The 103% of 260 is:

$260\times\frac{103}{100}=267.80.$

Now, notice that the interest is the difference between the original amount and the above result:

$I=267.80-260=7.80.$

Answer:

How much will you have to repay? $267.80.

How much of that was of interest? $7.80.