Math Problem Statement

Use the savings plan formula to answer the following question.

At age

39

you start saving or retirement. If your investment plan pays an APR of 77​% and you want to have

​$0.8 million when you retire in

26years, how much should you deposit​ monthly?

Solution

To solve this problem, we use the savings plan formula, which is:

A=P((1+r/n)nt1r/n)A = P \left( \frac{(1 + r/n)^{nt} - 1}{r/n} \right)

Where:

  • AA is the future value of the investment (in this case, $0.8 \text{ million} = 800,000 \text{ dollars})),
  • PP is the monthly deposit (what we're solving for),
  • rr is the annual interest rate (in decimal form),
  • nn is the number of times the interest is compounded per year (since it's monthly, n=12n = 12),
  • tt is the time in years (26 years).

Given:

  • A=800,000A = 800,000,
  • r=77%=0.77r = 77\% = 0.77,
  • n=12n = 12,
  • t=26t = 26.

We want to solve for PP. Let's plug these values into the formula and calculate it.The monthly deposit required is approximately $0.00019. This value seems unusually small given the high interest rate and long duration.

Let's break it down: an APR of 77% over 26 years significantly amplifies the growth of even a small deposit, which explains why the monthly contribution is minimal.

Do you want more details or have any questions?

Here are 5 related questions:

  1. What would the required monthly deposit be if the APR were 10% instead of 77%?
  2. How would changing the compounding period to quarterly affect the monthly deposit?
  3. What if you started saving 10 years earlier? How much would the monthly deposit change?
  4. How much would you save if you could only deposit half of the calculated amount monthly?
  5. What is the total amount you would contribute over 26 years compared to the final balance?

Tip: The higher the APR, the smaller the monthly deposit required for a given future amount.

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Math Problem Analysis

Mathematical Concepts

Savings Plans
Compound Interest
Future Value of Investments

Formulas

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

Theorems

Compound Interest Theorem

Suitable Grade Level

Grades 11-12, College Level