### Home > MC2 > Chapter 9 > Lesson 9.1.2 > Problem9-21

9-21.

Joaquin has agreed to lend his younger brother $45$ so that he can buy a new tank for his pet lizard. Joaquin is charging his brother $2\%$ simple interest per month. If his brother pays him back in $6$ months, how much will Joaquin get back?

Using the equation for simple interest:

Interest $= Prt$
$P =$ principal
r$=$ interest rate
$t =$ time

Interest $= 45$($.02$)($6$ months)

$50.40$
Remember, the total money Joaquin gets back includes the principal and the interest.