Question

sophia borrowed $12,109 at 4.5% simple interest for 6 months. How much will the interest amount to? What is the total amount that she will have to pay back at the end of 6 months?

Answer 1

The applicable formula is
  I = Prt
where P = the principal value (12109), r is the interest rate (0.045), and t is the time period in years (1/2)

a) Substituting the given values, the interest amount is computed as
  I = ($12,109)(.0.45)(1/2)
  I = $272.45

b) The amount Sophia will have to pay back is the sum of the principal amount and the interest owed.
  $12,109 + 272.45 = $12,381.45