Module: Your Options for Savings and Investing, Topic Application:
Making Money Grow
Problem Set 1
Justin invested $20,000 in his individual retirement account when he was 21 years old. He is
now 65 years old and ready to retire. He earned 5% interest on his account. Answer the
following questions about Justin’s account.
1. How many years did it take for the account to double? Use the Rule of 72 to make your
calculation.
14.4 years
2. How many years did Justin save?
44 years
3. How many times did Justin’s money double?
44/14.4 = 3.06 times
4. What is the value of Justin’s retirement account at age sixty-five?
$166,240
Problem Set 2
Amount Deposited
Interest Rate Earned
Years to Double
$15,000.00
4%
18
$23,000.00
5%
14.4
$25,000.00
7%
10.29
$30,000.00
10%
7.2