A customer pays the bank a total of 4 dollars comma 224 after borrowing 3 dollars comma 200 at a simple interest rate for 5 years. What was the interest rate?

First find the interest paid: $4,224 − $3,200 = $1,024. For simple interest, I = Prt, so r = I ÷ (Pt) = 1,024 ÷ (3,200 × 5) = 0.064. Converting 0.064 to a percent gives 6.4%, so the answer is 6.4 percent.

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