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91Ó°ÊÓ

Mike plans to make contributions to his retirement account for 15 years. After the last contribution, he will start withdrawing \(\$ 10,000\) a quarter for 10 years. Assuming Mike's account earns \(8 \%\) compounded quarterly, how large must his quarterly contributions be during the first 15 years, in order to accomplish his goal?

Short Answer

Expert verified
Mike must contribute approximately $2,368.05 quarterly.

Step by step solution

01

Determine the Future Value of Withdrawals

Mike wants to withdraw \(\\( 10,000\) every quarter for 10 years after the last contribution. First, let's calculate the total value of these withdrawals at the time he makes his last contribution. Since the account earns \(8\%\) annually, the quarterly rate is \((1+0.08/4)\). The withdrawals form an ordinary annuity where the withdrawal amount \(R = \\) 10,000\), the number of withdrawals \(n = 10 \times 4 = 40\), and the interest rate per period \(r = 0.08/4\). The future value \(FV\) of an ordinary annuity is calculated as follows:\[ FV = R \times \frac{{(1+r)^n - 1}}{r} \]Substitute the known values:\[ FV = 10,000 \times \frac{{(1+0.02)^{40} - 1}}{0.02} \]
02

Calculate Future Value of Withdrawals

Calculate the expression:\[ FV = 10,000 \times \frac{{(1.02)^{40} - 1}}{0.02} \]First, find \((1.02)^{40}\), which is approximately \(2.20804\). So\[ FV = 10,000 \times \frac{{2.20804 - 1}}{0.02} \]\[ FV = 10,000 \times \frac{1.20804}{0.02} \]\[ FV = 10,000 \times 60.402 \approx 604,020 \]Mike needs \(\$ 604,020\) at the time of his last contribution to meet his withdrawal needs.
03

Determine Present Value Needed at Last Contribution

Now, determine how much Mike needs to have in his account at his last contribution to have \(\$ 604,020\) by the time of the last withdrawal. Since this value needs to grow at an \(8\%\) annual rate (or \(2\%\) quarterly rate), use the present value formula of a single lump sum:\[ PV = \frac{FV}{(1+r)^n} \]where \(r = 0.02\) and \(n=40\).\[ PV = \frac{604,020}{(1+0.02)^{40}} \]
04

Calculate Present Value Needed

Substitute and calculate:\[ PV = \frac{604,020}{(1.02)^{40}} \]Given \((1.02)^{40} \approx 2.20804\),\[ PV \approx \frac{604,020}{2.20804} \approx 273,605 \]Mike must have \$273,605 in his account at the time of his last contribution.
05

Calculate Quarterly Contributions

Mike needs to accumulate \$273,605 through regular quarterly contributions over 15 years with compound interest. Use the future value of an annuity formula because contributions are made at the end of each period:\[ FV = PMT \times \frac{{(1+r)^n - 1}}{r} \]where \(FV = 273,605\), \(r = 0.02\), and \(n = 15 \times 4 = 60\). Solve for \(PMT\):\[ 273,605 = PMT \times \frac{{(1.02)^{60} - 1}}{0.02} \]
06

Solve for Quarterly Contribution

Calculate the necessary values and solve for \(PMT\):First calculate \((1.02)^{60}\), which is approximately \(3.310204\).\[ 273,605 = PMT \times \frac{3.310204 - 1}{0.02} \]\[ 273,605 = PMT \times \frac{2.310204}{0.02} \]\[ 273,605 = PMT \times 115.5102 \]\[ PMT = \frac{273,605}{115.5102} \approx 2,368.05 \]Mike's quarterly contribution must be approximately \$2,368.05.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Future Value of Annuity
When planning for retirement, understanding the future value of an annuity is crucial. It helps you know how much your regular contributions will grow over time. An annuity is a series of equal payments made at regular intervals. In this context, imagine consistently saving money every quarter into a retirement account.

The formula for calculating the future value of an annuity is given by:\[FV = R \times \frac{{(1 + r)^n - 1}}{r}\]Where:
  • \(FV\) stands for "Future Value" of the annuity.
  • \(R\) is the regular contribution or withdrawal amount.
  • \(r\) is the interest rate per period.
  • \(n\) is the total number of payments or withdrawals.
This formula considers how each payment grows with each compounding period until the final date. By finding the future value, you can determine how much your savings will amount to when it's time to retire. It's a great way to see your money grow over time.
Present Value
The concept of present value helps determine how much you need to invest now to reach a desired amount in the future. It's an essential tool in retirement planning since it helps ensure your future financial needs will be met. Present value is particularly useful when you have a specific goal, like Mike's future withdrawal plan.

The formula for present value (PV) of a future sum is:\[PV = \frac{FV}{(1 + r)^n}\]Where:
  • \(PV\) indicates the amount you need today.
  • \(FV\) is the future sum you want.
  • \(r\) is the interest rate per period.
  • \(n\) is the number of compounding periods until the future date.
By using present value, you reverse calculate to find out how much to set aside now to achieve your retirement dreams. It allows you to plan effectively by knowing exactly what is required today to secure future withdrawals.
Compound Interest
Compound interest is a powerful concept in finance that affects how savings grow over time. Unlike simple interest, which earns interest on only the initial principal, compound interest earns on both the initial principal and the accumulated interest.

This means your money grows at an accelerating rate, thanks to the interest-on-interest effect. The process can be broken down using the formula:\[A = P \times (1 + r)^n\]Where:
  • \(A\) represents the amount after compounding.
  • \(P\) is the initial principal.
  • \(r\) is the interest rate per period.
  • \(n\) is the total number of compounding periods.
In retirement planning, compound interest allows regular contributions to accumulate into substantial amounts. By understanding how compound interest works, you can make informed decisions about your investments and set yourself up for a comfortable retirement.
Finance Mathematics
Finance mathematics is the backbone of understanding retirement planning and other financial decisions. It encompasses various formulas and concepts that help quantify how money can grow over time, as well as the cost of loans and investments.

Knowledge of finance mathematics enables you to utilize tools, such as the aforementioned future and present value formulas, tailor investment strategies, and manage your finances effectively. It simplifies complex financial dealings by applying mathematical principles, aiding in clear decision making.

Core concepts like future value of annuities, present value, and compound interest are fundamental elements of finance mathematics. By learning these, you equip yourself with the skills to not only prepare for retirement but also plan any financial goal you may have. This understanding is critical for developing a sustainable financial strategy.

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Most popular questions from this chapter

Suppose you are looking to buy a \(\$ 5000\) face value 26 -week T-bill. If you want to earn at least \(1 \%\) annual interest, what is the most you should pay for the T-bill?

Lynn bought a \(\$ 300,000\) house, paying \(10 \%\) down, and financing the rest at \(6 \%\) interest for 30 years. a. Find her monthly payments. b. How much interest will she pay over the life of the loan?

Jose has determined he needs to have \(\$ 800,000\) for retirement in 30 years. His account earns \(6 \%\) interest. a. How much would he need to deposit in the account each month? b. How much total money will he put into the account? c. How much total interest will he earn?

Suppose that 10 years ago you bought a home for \(\$ 110,000\), paying \(10 \%\) as a down payment, and financing the rest at \(9 \%\) interest for 30 years. a. Let's consider your existing mortgage: i. How much money did you pay as your down payment? ii. How much money was your mortgage (loan) for? iii. What is your current monthly payment? iv. How much total interest will you pay over the life of the loan? b. This year, you check your loan balance. Only part of your payments have been going to pay down the loan; the rest has been going towards interest. You see that you still have \(\$ 88,536\) left to pay on your loan. Your house is now valued at \(\$ 150,000\). i. How much of the loan have you paid off? (i.e., how much have you reduced the loan balance by? Keep in mind that interest is charged each month - it's not part of the loan balance.) ii. How much money have you paid to the loan company so far? iii. How much interest have you paid so far? iv. How much equity do you have in your home (equity is value minus remaining debt) c. Since interest rates have dropped, you consider refinancing your mortgage at a lower \(6 \%\) rate. i. If you took out a new 30 year mortgage at \(6 \%\) for your remaining loan balance, what would your new monthly payments be? ii. How much interest will you pay over the life of the new loan? d. Notice that if you refinance, you are going to be making payments on your home for another 30 years. In addition to the 10 years you've already been paying, that's 40 years total. i. How much will you save each month because of the lower monthly payment? ii. How much total interest will you be paying (you need to consider the amount from \(2 \mathrm{c}\) and \(3 \mathrm{~b}\) ) iii. Does it make sense to refinance? (there isn't a correct answer to this question. Just give your opinion and your reason)

A friend bought a house 15 years ago, taking out a \(\$ 120,000\) mortgage at \(6 \%\) for 30 years, making monthly payments. How much does she still owe on the mortgage?

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