Simple Interest SWBAT find simple interest ; find the total amount earned or due; find the rate of interest; find the time that principal is left on deposit

Definitions Principal the amount of money borrowed or deposited the amount of money borrowed or depositedInterest The amount earned or paid in exchange for the use of money The amount earned or paid in exchange for the use of money Simple interest Interest earned or paid only on the principal for a stated period of time Interest earned or paid only on the principal for a stated period of time Rate of interest The percent of interest paid or earned The percent of interest paid or earnedTime How long in years the principal is borrowed or left on deposit How long in years the principal is borrowed or left on deposit

Simple Interest Formula Interest = principal x rate x time I = prt

Think Christian borrowed $2500 from his parents for a dirt bike. He agreed to repay the money with an interest rate of 5.5% per year. How much money will he pay back at the end of the 3 years?

Examples $800 at an annual rate of 8% for 9 months $720 at an annual rate of 8.5% for 6 months $200 borrowed for 2 years with $24 of interest $400 deposited for 9 months with $24 of interest $350 at 8% per year with $84 of interest $800 at 7% per year with $42 in interest

Examples Elyssa has $365. If she deposits that money for 24 months and earns $36.50 what is the annual rate that is earned? Allie borrowed $1100 at an interest rate of 6% per year. If she paid interest of $297, for how many years did she take out the loan?

Try These $500 at 5% for 4 years I = 500 ·.05 · 4 I = 500 ·.05 · 4 I = $100 I = $100 $1800 for 2 years, $144 interest 144 = 1800 · r · = 1800 · r · = 3600r 144 = 3600r R =.04 R =.04 4% 4% $900 at 9%, $243 interest 243 = 900 ·.09 · t 243 = 900 ·.09 · t 243 = 81t 243 = 81t T = 3 years T = 3 years