How saving a little each month grows: simple and compound interest

Answer Key - Grade 8 Math Worksheet

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

1. Read this first

   Growth table

   Year	Balance
   0	$1,000
   1	$1,100
   2	$1,210

2. 1.

   Ari reads the table for Ms. Frost's pretend account. It earns the same percent each year and gets no deposits. If the pattern continues, what will its balance be in year 4?

   $1,464.10
3. 2.

   Bo reads the table for the class trip fund. It earns the same percent each year and gets no deposits. If the pattern continues, what will its balance be in year 4?

   $1,036.80
4. 3.

   Esme reads the table for Mr. Cole's pretend account. It earns the same percent each year and gets no deposits. If the pattern continues, what will its balance be in year 4?

   $439.23
5. 4.

   Jun reads the table for the class garden fund. It earns the same percent each year and gets no deposits. If the pattern continues, what will its balance be in year 4?

   $518.40
6. 5.

   Kira watches two pretend accounts that each start with $1,200 and get no deposits. One earns 10% simple interest, the other 10% compound. After 3 years, how much more is in the compound account?

   $37.20
7. 6.

   Luz watches two pretend accounts that each start with $400 and get no deposits. One earns 20% simple interest, the other 20% compound. After 3 years, how much more is in the compound account?

   $51.20
8. 7.

   Milo watches two pretend accounts that each start with $900 and get no deposits. One earns 10% simple interest, the other 10% compound. After 3 years, how much more is in the compound account?

   $27.90
9. 8.

   Noah watches Ms. Shaw's pretend account. It holds $600 and earns 5% simple interest a year, with no deposits. In how many years will it hold $840?

   8
10. 9.

    Ren watches Mr. Grove's pretend account. It holds $1,500 and earns 4% simple interest a year, with no deposits. In how many years will it hold $2,040?

    9

11. Growth table, balances rounded to the dollar

    Plan	Monthly deposit	Years	Total deposited	Balance at the end
    X	$20	30	$7,200	≈ $20,191
    Y	$60	10	$7,200	≈ $9,882

12. 10.

    Tala reads two pretend retirement plans for Ms. Frost, both at 6% a year, compounded monthly. Both deposit the same total. How much more interest does Plan X earn than Plan Y?

    $10,309