Math Problem Statement

Ethan is saving up money to buy a car. Ethan puts $8,000.00 into an account which earns 4% interest, compounded monthly. How much will he have in the account after 6 years? Use the formula A=P1+ r n nt, where A is the balance (final amount), P is the principal (starting amount), r is the interest rate expressed as a decimal, n is the number of times per year that the interest is compounded, and t is the time in years. Round your answer to the nearest cent. $

Solution

To calculate how much Ethan will have in the account after 6 years, we use the compound interest formula:

A=P(1+rn)ntA = P \left(1 + \frac{r}{n}\right)^{nt}

Where:

  • AA is the final amount (balance in the account)
  • P=8000P = 8000 is the principal (initial amount)
  • r=0.04r = 0.04 is the annual interest rate (4% as a decimal)
  • n=12n = 12 is the number of times the interest is compounded per year (monthly)
  • t=6t = 6 is the time in years

Now, plug the values into the formula:

A=8000(1+0.0412)12×6A = 8000 \left(1 + \frac{0.04}{12}\right)^{12 \times 6}

Let's break this down step by step:

  1. Calculate 0.0412=0.003333\frac{0.04}{12} = 0.003333.
  2. Add 1: 1+0.003333=1.0033331 + 0.003333 = 1.003333.
  3. Multiply the exponent: 12×6=7212 \times 6 = 72.
  4. Now raise 1.0033331.003333 to the power of 72: 1.003333721.270241.003333^{72} \approx 1.27024
  5. Multiply the principal by this value: A=8000×1.2702410162.00A = 8000 \times 1.27024 \approx 10162.00

Thus, the final balance in the account after 6 years is $10,162.00.

Let me know if you'd like a more detailed breakdown of any step! Here are some related questions to expand your understanding:

  1. How would the balance change if the interest rate were higher, say 5% instead of 4%?
  2. What happens to the balance if the interest were compounded daily instead of monthly?
  3. How would the final amount differ if Ethan invested the money for 10 years instead of 6 years?
  4. What is the effect of changing the principal from $8,000 to $10,000?
  5. What would the formula look like if the interest were compounded quarterly instead of monthly?

Tip: The more frequently interest is compounded, the more you’ll end up with in the long run!

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Math Problem Analysis

Mathematical Concepts

Compound Interest
Exponents
Decimal Operations

Formulas

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

Theorems

Compound Interest Theorem

Suitable Grade Level

Grades 9-11