Math Problem Statement

Emma Gilger placed $24,000 in a 10-year account paying 5.0% interest compounded quarterly.  The credit union where she placed her money pays a rate of 2.5% compounded daily on simple savings accounts.  If she withdraws $8000 of the original deposit after 18 months, answer the following questions.  Assume each month is 30 days.

Solution

Let's break down this scenario step by step:

Information provided:

  1. Initial Deposit (Principal): $24,000
  2. Interest rate for the 10-year account: 5.0% compounded quarterly
  3. Interest rate for simple savings account: 2.5% compounded daily
  4. Withdrawal: $8,000 after 18 months
  5. Time Period for Calculation: 18 months, with each month assumed to have 30 days.

We need to answer various questions about how much Emma's money will grow or change after 18 months of deposit and withdrawal. Let’s go step-by-step:


1. Compound Interest Calculation for the 10-Year Account (Quarterly Compounding)

We will use the formula for compound interest, which is:

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

Where:

  • AA is the amount after interest
  • PP is the principal amount (initial deposit)
  • rr is the annual interest rate (decimal form)
  • nn is the number of times interest is compounded per year
  • tt is the number of years the money is invested for

For this case:

  • P=24,000P = 24,000
  • r=0.05r = 0.05 (5%)
  • n=4n = 4 (since it's compounded quarterly)
  • t=1.5t = 1.5 years (18 months)

Step 1: Calculate the amount after 18 months with the 10-year account.

Let me do the calculation. Given values for compound interest calculation P = 24000 # Initial deposit r = 0.05 # Annual interest rate n = 4 # Compounded quarterly t = 1.5 # Time period in years (18 months)

Compound interest formula: A = P(1 + r/n)^(nt)

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

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Math Problem Analysis

Mathematical Concepts

Compound Interest
Simple Interest
Exponential Growth
Financial Mathematics

Formulas

Compound Interest Formula: A = P(1 + r/n)^(nt)
Simple Interest Formula: A = P(1 + rt)

Theorems

Compound Interest Theorem
Simple Interest Calculation

Suitable Grade Level

Grades 9-12