Math Problem Statement

$8000 are invested in a bank account at an interest rate of 10 percent per year. Find the amount in the bank after 11 years if the interest is compounded annually, quarterly, monthly, and continuously.

Solution

Let's solve each of these cases step by step.

The formula for compound interest is:

1. Compound Interest (Discrete Compounding)

A=P(1+rn)ntA = P \left(1 + \frac{r}{n}\right)^{n \cdot t} Where:

  • AA = Amount after tt years
  • PP = Principal amount = $8000
  • rr = Annual interest rate = 10% = 0.10
  • nn = Number of compounding periods per year
  • tt = Time in years = 11

1.1. Compounded Annually (n=1n = 1):

A=8000(1+0.101)111A = 8000 \left(1 + \frac{0.10}{1}\right)^{1 \cdot 11}

1.2. Compounded Quarterly (n=4n = 4):

A=8000(1+0.104)411A = 8000 \left(1 + \frac{0.10}{4}\right)^{4 \cdot 11}

1.3. Compounded Monthly (n=12n = 12):

A=8000(1+0.1012)1211A = 8000 \left(1 + \frac{0.10}{12}\right)^{12 \cdot 11}


2. Compound Interest (Continuous Compounding)

For continuous compounding, the formula is: A=PertA = P \cdot e^{r \cdot t} Where:

  • ee is the mathematical constant (approximately 2.718)

2.1. Continuous Compounding:

A=8000e0.1011A = 8000 \cdot e^{0.10 \cdot 11}


Let me calculate each value for you. Given values P = 8000 # Principal r = 0.10 # Annual interest rate (10%) t = 11 # Time in years

Compounding frequencies

n_annual = 1 # Annual compounding n_quarterly = 4 # Quarterly compounding n_monthly = 12 # Monthly compounding

Continuous compounding uses the exponential function

import math

Calculations

A_annual = P * (1 + r / n_annual) ** (n_annual * t) # Annually A_quarterly = P * (1 + r / n_quarterly) ** (n_quarterly * t) # Quarterly A_monthly = P * (1 + r / n_monthly) ** (n_monthly * t) # Monthly A_continuous = P * math.exp(r * t) # Continuous

A_annual, A_quarterly, A_monthly, A_continuousHere are the results for each scenario:

  1. Compounded Annually: $22,824.93
  2. Compounded Quarterly: $23,710.46
  3. Compounded Monthly: $23,924.03
  4. Compounded Continuously: $24,033.33

Would you like further details on how these were calculated or need additional assistance?

Related Questions:

  1. What would the amount be if the principal was $10,000 instead of $8,000?
  2. How does increasing the interest rate to 12% affect the results?
  3. What happens if the investment period is reduced to 5 years?
  4. How does the number of compounding periods per year influence the final amount?
  5. How does continuous compounding differ mathematically from discrete compounding?

Tip:

The more frequently interest is compounded, the higher the total amount due to the effect of earning "interest on interest." Continuous compounding provides the theoretical maximum return.

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Math Problem Analysis

Mathematical Concepts

Compound Interest
Exponential Growth
Continuous Compounding

Formulas

A = P(1 + r/n)^(n*t)
A = P * e^(r*t)

Theorems

Compound Interest Formula
Exponential Function Properties

Suitable Grade Level

Grades 9-12