Simple Interest Worksheets
Free printable simple interest worksheets. Use I = Prt to find the interest on money saved or borrowed, to the cent. Answer key included.
Each question gives an amount of money, an interest rate and a number of years, and asks for the interest: $350 saved at 4.5% simple interest for 3 years earns $47.25. Some questions save the money and some borrow it, and the formula is the same either way. It is I = Prt - the principal, times the rate as a decimal, times the time in years: 350 × 0.045 × 3.
Principals are whole tens of dollars from $130 to $500, rates run from 1% to 8% in steps of half a percent, and the time is 2 to 10 whole years. The answer is the interest alone, not the new balance, and it always comes out to the cent.
What this worksheet covers
- Find simple interest using the formula I = Prt
- Write an interest rate as a decimal to use in a formula
Common Core standards
- 7.RP.A.3 Use proportional relationships to solve multistep ratio and percent problems, including percent increase and decrease.
Frequently asked questions
What is simple interest?
Interest paid only on the original amount. $200 at 5% earns $10 every year, so after 4 years it has earned $40. Compound interest, where the interest also earns interest, is not on these sheets.
Why does 4.5% become 0.045?
A percent is a number out of 100, so 4.5% is 4.5 ÷ 100 = 0.045. Putting 4.5 into the formula instead gives an answer 100 times too big, which is a common slip on these sheets.
How do I find the total after interest?
Add the interest to the principal: $350 that earns $47.25 grows to $397.25. The answer key gives the interest only, because that is what I = Prt finds.
What grade is simple interest?
Seventh grade, as one of the percent problems in the ratio standard. Interest over months, and compound interest, come later.