Tommy Blox borrowed $4000 from a bank at 12% simple interest. After 3 years, he paid back the loan plus the interest. How much did Tommy pay back altogether?

The formula we'll use for this is the simple interest formula, or:

Where:

P is the principal amount, $4000.00.

r is the interest rate, 12% per year, or in decimal form, 12/100=0.12.

t is the time involved, 3 ... year (s) time periods.

So, t is 3 ... year time periods.

To find the simple interest, we multiply 4000 * 0.12 * 3 to get that:

The interest is: $1440.00