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Suppose P dollars is invested at 5% annual interest compounded quarterly. How many years will it take for the money to double?

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Answer:

It will take approximately 14.2 years for the money to double at a 5% annual interest rate compounded quarterly.

Explanation:

To determine how many years it will take for the money to double, we can use the formula for compound interest:

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

where A is the final amount, P is the principal amount (initial investment), r is the annual interest rate (as a decimal), n is the number of times interest is compounded per year, and t is the number of years.

In this case, the final amount is twice the initial investment (2P), the annual interest rate is 5% (or 0.05 as a decimal), and interest is compounded quarterly (n = 4).

Let's substitute these values into the formula and solve for t:

2P = P(1 + 0.05/4)^(4t)

Cancelling out the P:

2 = (1 + 0.05/4)^(4t)

Now, we can solve for t by taking the logarithm of both sides:

log(2) = log((1 + 0.05/4)^(4t))

Using the logarithmic property:

log(2) = 4t * log(1 + 0.05/4)

Now, isolate t:

t = (log(2)) / (4 * log(1 + 0.05/4))

On solving the above equation, we get,

t ≈ 14.2 years

Therefore, it will take approximately 14.2 years for the money to double at a 5% annual interest rate compounded quarterly.

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