oday is Derek’s 25th birthday. Derek has been advised that he needs to have $3,816,699.00 in his retirement account the day he turns 65. He estimates his retirement account will pay 10.00% interest. Assume he chooses not to deposit anything today. Rather he chooses to make annual deposits into the retirement account starting on his 29.00th birthday and ending on his 65th birthday. How much must those deposits be?

1 answer

To determine the amount of annual deposits Derek needs to make into his retirement account starting on his 29th birthday and ending on his 65th birthday (for a total of 37 years of deposits), we can use the future value of an ordinary annuity formula.

The future value \( FV \) of an ordinary annuity can be calculated using the formula:

\[ FV = P \times \frac{(1 + r)^n - 1}{r} \]

Where:

  • \( FV \) is the future value of the annuity (in this case, $3,816,699.00).
  • \( P \) is the annual deposit (what we are trying to find).
  • \( r \) is the annual interest rate (10.00% or 0.10).
  • \( n \) is the number of deposits (from age 29 to age 65 is 37 years).

Rearranging the formula to solve for \( P \):

\[ P = \frac{FV}{\frac{(1 + r)^n - 1}{r}} \]

Plugging in the values:

  • \( FV = 3,816,699.00 \)
  • \( r = 0.10 \)
  • \( n = 37 \)

We first calculate \( (1 + r)^n \):

\[ (1 + 0.10)^{37} = 1.10^{37} \]

Calculating \( 1.10^{37} \):

\[ 1.10^{37} \approx 14.35 \]

Now, plug this value back into the formula:

\[ \frac{(1 + r)^n - 1}{r} = \frac{14.35 - 1}{0.10} = \frac{13.35}{0.10} = 133.5 \]

Now substitute this value into the equation for \( P \):

\[ P = \frac{3,816,699.00}{133.5} \approx 28,528.96 \]

Thus, the annual deposit Derek needs to make is approximately:

\[ \boxed{28,528.96} \]

So, Derek must make annual deposits of about $28,528.96 starting on his 29th birthday until he turns 65 to reach his retirement goal of $3,816,699.00.