Compound interest with a formula

Answer Key - Grade 9 Math Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   Mr. Dunn puts $2,500 in a pretend account at 4% a year, compounded quarterly, for 3 years. Noah uses A = P(1 + r/n)^(nt). To the nearest cent, what is the balance?

   $2,817.06
2. 2.

   Ms. Shaw puts $5,000 in a pretend account at 2% a year, compounded quarterly, for 4 years. Tala uses A = P(1 + r/n)^(nt). To the nearest cent, what is the balance?

   $5,415.36
3. 3.

   The class pretend fund holds $800 at 4% a year, compounded monthly, for 3 years. Zee wants only the interest. To the nearest cent, how much interest is earned?

   $101.82
4. 4.

   Mr. Grove's pretend account holds $1,500 at 6% a year, compounded quarterly, for 2 years. Ari wants only the interest. To the nearest cent, how much interest is earned?

   $189.74
5. 5.

   Ms. Wells's pretend account holds $300 at 5% a year, compounded twice a year, for 4 years. Bo wants only the interest. To the nearest cent, how much interest is earned?

   $65.52
6. 6.

   The art club's pretend fund holds $2,000 at 3% a year, compounded monthly, for 5 years. Esme wants only the interest. To the nearest cent, how much interest is earned?

   $323.23
7. 7.

   Mr. Cole puts $750 in a pretend account at 3% a year, compounded monthly, for 4 years. Jun checks the formula. Which one gives the balance?

   • A = 750(1 + 0.03/12)^(12 · 4)
   • A = 750(1 + 0.03)^(12 · 4)
   • A = 750(1 + 0.03/12)^4
   • A = 750(1 + 3/12)^(12 · 4)
8. 8.

   Ms. Reyes puts $1,200 in a pretend account at 4% a year, compounded quarterly, for 5 years. Kira checks the formula. Which one gives the balance?

   • A = 1200(1 + 0.04/4)^5
   • A = 1200(1 + 0.04/4)^(4 · 5)
   • A = 1200(1 + 4/4)^(4 · 5)
   • A = 1200(1 + 0.04)^(4 · 5)
9. 9.

   The class puts $500 in a pretend account at 6% a year, compounded twice a year, for 3 years. Luz checks the formula. Which one gives the balance?

   • A = 500(1 + 0.06)^(2 · 3)
   • A = 500(1 + 6/2)^(2 · 3)
   • A = 500(1 + 0.06/2)^3
   • A = 500(1 + 0.06/2)^(2 · 3)
10. 10.

    Mr. Vance puts $2,000 in a pretend account at 5% a year, compounded monthly, for 2 years. Milo checks the formula. Which one gives the balance?

    • A = 2000(1 + 5/12)^(12 · 2)
    • A = 2000(1 + 0.05)^(12 · 2)
    • A = 2000(1 + 0.05/12)^(12 · 2)
    • A = 2000(1 + 0.05/12)^2