Math Problem Statement

You estimate that you will need about $80,000 to send you child to college in eight years. You have about $35,000. At what rate will you just reach your goal?

Solution

To find the rate of return that will allow you to grow your $35,000 to $80,000 in eight years, we can use the formula for compound interest:

A=P(1+r)tA = P(1 + r)^t

Where:

  • AA is the final amount ($80,000),
  • PP is the initial amount ($35,000),
  • rr is the annual interest rate (expressed as a decimal),
  • tt is the time in years (8 years).

We want to solve for rr. Let's plug in the known values:

80,000=35,000(1+r)880,000 = 35,000(1 + r)^8

First, divide both sides by 35,000:

80,00035,000=(1+r)8\frac{80,000}{35,000} = (1 + r)^8

Simplifying:

2.2857(1+r)82.2857 \approx (1 + r)^8

Now, take the 8th root of both sides to solve for rr:

1+r=2.285781 + r = \sqrt[8]{2.2857}

r=2.285781r = \sqrt[8]{2.2857} - 1

Let's calculate the value of rr.The required annual interest rate to grow your $35,000 to $80,000 in eight years is approximately 10.89%.

Would you like more details on how the calculation was done, or do you have any questions?

Here are five related questions you might find interesting:

  1. What happens if the rate of return is lower than 10.89%?
  2. How does the interest rate affect the time needed to reach $80,000?
  3. What if you start with a different amount, say $40,000?
  4. How does compounding frequency (monthly vs. yearly) impact the growth?
  5. What strategies can help achieve a higher return on investment?

Tip: It's important to account for inflation when planning for future expenses like college tuition.

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Math Problem Analysis

Mathematical Concepts

Compound Interest
Exponential Growth

Formulas

A = P(1 + r)^t

Theorems

Compound Interest Formula

Suitable Grade Level

Grades 10-12