Question

You borrow money for 4 years. The total amount that you repay is $7,840, which includes $840 in simple interest. How much was the principal? What was the annual interest rate?

Answer 1

• principal: $7000
• interest rate: 3%

Explanation:

amount repaid = principal + interest

$7840 = principal + $840

$7000 = principal . . . . . . . . subtract $840 from both sides of the equation

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I = Prt

840 = 7000·r·4

840/(4·7000) = r = 0.03 = 3%

The principal was $7000; the interest rate was 3%.