Worksheet Generator · Investing
Rule of 72 Worksheet Generator
Make printable Rule of 72 practice, fresh every time. Students divide 72 by a rate of return to estimate how long money takes to double, work backwards to find the rate a goal needs, and follow a balance through several doublings. Choose 4 to 15 questions, keep the rates to ones that divide 72 evenly so every answer is a whole number of years, and print with a built-in answer key that shows the division. Included with your full Money Instructor membership.
Make a Worksheet
Build your Rule of 72 worksheet
How It Works
Make a worksheet in four steps
- Choose the question type. Years to double, the rate a goal needs, growth over several doublings — or a mix of all three.
- Choose the rates. Leave rates that divide 72 evenly on for whole-number answers (the mental-math version), or turn it off for any whole rate and one-decimal answers.
- Generate. Press Generate worksheet for a fresh set of questions and numbers.
- Print or grade. Keep Include answer key on to print a completed copy showing the division for every item, or press ↻ New version for a new set.
In the Classroom
Six ways to use it
Estimating doubling time
72 ÷ rate, done in your head — the skill the rule exists for.
Working backwards
Given a target number of years, what rate would it actually take?
Seeing compounding
A balance doubling two or three times, and how many years that really is.
Mental math practice
Rates that divide 72 evenly turn this into clean division without a calculator.
Bell ringers & warm-ups
Four questions is a five-minute opener; fifteen is a full practice sheet.
Sub plans & homeschool
No-prep and self-checking, with a fresh set of numbers every time.
What It Teaches
Money skills students build
Most interest worksheets run forwards: here is a balance, a rate and a number of years, now find the total. The Rule of 72 runs the other way — it starts from the rate and asks how long, which is the question people actually ask about their own money. It is also the rare piece of finance arithmetic a student can do without a calculator, which is exactly why it has survived since 1494. Pair it with the Rule of 72 explained, which sets the estimate beside the exact answer at every rate, and where the rule came from.
- Estimate doubling time from a rate of return using 72 ÷ rate
- Work backwards to the rate a doubling goal would need
- Follow a balance through two or three doublings and total the years
- Recognise that the rule is an estimate, not an exact answer
- Do finance arithmetic without a calculator
Common Questions
Rule of 72 Worksheet FAQ
Do I need a membership to use this generator?
Yes — the generator is a full Money Instructor membership feature (the paid plan, not a free account). Full members can make and print unlimited worksheets with answer keys. The page itself is free to read.
What is the Rule of 72?
Divide 72 by an annual rate of return and you get roughly the number of years it takes for money to double. At 6% a year, 72 ÷ 6 = 12 years. It works in reverse too: to double in 8 years you would need about 72 ÷ 8 = 9% a year. The full explanation is here.
Why do the rates default to 2, 3, 4, 6, 8, 9 and 12?
Because those divide 72 evenly, so every answer is a whole number of years and students can do the division in their heads — which is the entire point of the rule. Turn rates that divide 72 evenly off and the generator uses any whole rate, so answers may carry one decimal (72 ÷ 5 = 14.4). That is a genuinely harder exercise, not just a different one.
Does the worksheet show the exact answer as well?
No, and that is deliberate. The exact figure needs a logarithm and a calculator, which is the opposite of the skill this sheet practises. If you want students to compare the estimate with the true answer, the Rule of 72 article carries a doubling table that sets the two side by side at thirteen different rates.
Is there an answer key?
Yes. Keep Include answer key on and the tool prints a completed copy showing the division used for every question. Set Number of worksheets up to 5 for different versions of the same practice.
What grades is this for?
Grades 7–12 and adult education. With the even-divisor rates on, the arithmetic is simple division and works from about grade 7; the growth-over-several-doublings questions suit older students, and turning the even-divisor option off adds decimal division for high school.
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