Math Problem Statement

Mike deposited $30,000 in a saving account in which interest is compounded continuously. The annual rate of interest is 5%. How much does he have in this account after 18 years? Round your answer to the nearest cent.

Solution

The question you're working on involves calculating the amount in a savings account after 18 years, with interest compounded continuously.

The formula for continuous compounding is:

A=PertA = P \cdot e^{rt}

where:

  • AA is the amount after time tt,
  • PP is the principal amount (initial deposit),
  • rr is the annual interest rate (as a decimal),
  • tt is the time the money is invested (in years),
  • ee is the base of the natural logarithm (approximately 2.71828).

From the image:

  • P=30000P = 30000,
  • r=5%=0.05r = 5\% = 0.05,
  • t=18t = 18 years.

Now, we calculate AA:

A=30000e0.0518A = 30000 \cdot e^{0.05 \cdot 18}

A=30000e0.9A = 30000 \cdot e^{0.9}

A=300002.4596(usinge0.92.4596)A = 30000 \cdot 2.4596 \quad (\text{using} \, e^{0.9} \approx 2.4596)

A300002.4596=73788A \approx 30000 \cdot 2.4596 = 73788

Rounding to the nearest cent:

A73788.08A \approx 73788.08

So, the correct amount after 18 years should be $73,788.08, not $73,787.96 as shown.

Would you like any further clarifications or detailed steps?


Here are 5 related questions:

  1. How does continuous compounding differ from annual compounding?
  2. What would be the total amount if the interest rate were 6% instead of 5%?
  3. How would you calculate the amount after 25 years instead of 18 years?
  4. What is the formula for compound interest when it's compounded annually instead of continuously?
  5. How would changes in the principal amount affect the final balance?

Tip: Continuous compounding grows your money faster because it assumes the interest is added instantly and continuously, unlike annual or monthly compounding.

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Math Problem Analysis

Mathematical Concepts

Continuous Compounding
Exponential Growth
Interest Calculation

Formulas

A = P * e^(rt)

Theorems

Continuous Compounding Formula

Suitable Grade Level

Grades 11-12