### Home > MC2 > Chapter Ch9 > Lesson 9.1.2 > Problem 9-21

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? Homework Help ✎

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.