Rule of 72

A quick way to estimate how long it takes for your money to double is called ________.

• the rule of 72

• compound interest

• simple interest

• inflation

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CCSS.HSF.LE.A.1

CCSS.HSF.LE.A.2

CCSS.HSF.LE.A.3

CCSS.HSF.LE.B.5

Rule: 72 divided by the interest rate is the time in years it will take your money to double. 72 / r = y
Your rate of return (or interest rate) is 9% a year. How long before your investment doubles?
Do 72 / 9 =

• 9 years
• 8 years
• 7 years
• They won't

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CCSS.HSA.CED.A.1

CCSS.HSA.REI.B.3

Your interest rate is 6% a year. How long before your investment doubles? You area looking for y.
72/r = y

• 18 years
• 16 years
• 12 years
• 8 years

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CCSS.HSF.LE.A.4

Your interest rate is 1% a year because they are in a savings account. How long before your savings doubles?
72 / r = y

• 72 years
• 36 years
• 1 year
• They will never double

Tags

CCSS.HSF.LE.A.4

How many years will it take $600 to double with 10% interest? The amount of money does not matter.
72/r = y (<-- no amount of money in this equation)

• 6 years
• 8.3 years
• 10 years
• 7.2 years

Tags

CCSS.HSF.LE.A.4

What interest rate would you need to double $2500 in 12 years?

72/r = y 72/r = 12 You are looking for r so 72/12 = r

• 5%
• 6%
• 34%
• 16%

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CCSS.6.EE.B.7

How many years will it take to double your money with a 3% interest rate?

• 24 years
• 12 years
• 4 years
• none of these

Tags

CCSS.HSF.LE.A.4

What calculation should you do to answer the question:

How many years will it take $900 to double if the interest rate is 2%?

• 72 / 2

• 900 / 2

• 2 / 100 · 900

• 72 · 2

Tags

CCSS.HSF.LE.A.4

When interest is gained on interest, this is called...

• simple interest

• compound interest

• rule of 72

• inflation

Tags

CCSS.HSF.LE.A.1

CCSS.HSF.LE.A.2

CCSS.HSA.SSE.A.1

CCSS.HSF.BF.A.1

If Becca has money in the bank at 1% interest, how many years will it take her money to double? (type number only)

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CCSS.HSF.LE.A.4