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A principal of $600 earns 3.2% interest compounded monthly. What is the effective interest (growth) rate? (Hint: make the equation look like abt.) About how long does it take to reach $1000?

A principal of $600 earns 3.2% interest compounded monthly. What is the effective-example-1
User Weicheng
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1 Answer

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13 votes

Answer:

Step-by-step explanation:

The formula for calculating the effective interest rate is expressed as

R = (1 + i/n)^n - 1

where

R is the effective interest rate

i is the nominal rate

n is the number of compounding periods in a year

From the information given,

n = 12 because it was compounded monthly

i = 3.2% = 3.2/100 = 0.032

Thus,

R = (1 + 0.032/12)^12 - 1

R = 0.03247

Multiplying by 100, it becomes 0.03247 x 100

Effective interest rate = 3.25%

We would apply the formula for calculating compound interest which is expressed as

A = a(1 + r/n)^nt

where

a is the principal or initial amount

t is the number of years

A is the final amount after t years

From the information given,

A = 1000

a = 600

n = 12

We want to find t

By substituting these values into the formula, we have

1000 = 600(1 + 0.032/12)^12t

1000/600 = (1.00267)^12t

Taking natural log of both sides, we have

ln (1000/600) = ln (1.00267)^12t = 12tln(1.00267)

12t = [ln (1000/600)]/ln (1.00267) = 191.5758

t = 191.5758/12

t = 16

It takes 16 years for the amount to reach $1000

User Allocated
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