Math Problem Statement

Complete the table below by finding the unknowns, including the principal, rate, and compound interest, based on given values in a compound interest table.

Solution

To complete the table and find the unknowns, we need to use the compound interest formula:

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

Where:

  • FF is the future value,
  • PP is the principal,
  • rr is the annual interest rate (expressed as a decimal),
  • tt is the time in years,
  • nn is the number of times interest is compounded per year (for simplicity, we'll assume it's compounded annually, i.e., n=1n = 1),
  • Ic=FPI_c = F - P is the compound interest.

Now let's solve the missing values step by step:

First Row:

Given:

  • Principal P=8,000P = 8,000,
  • Time t=5t = 5 years,
  • Future Value F=12,593.91F = 12,593.91.

We need to find the Rate rr and Compound Interest IcI_c.

Step 1: Find Rate rr

Using the formula:

12,593.91=8,000(1+r)512,593.91 = 8,000 \left(1 + r\right)^5

12,593.918,000=(1+r)5\frac{12,593.91}{8,000} = (1 + r)^5

1.57423875=(1+r)51.57423875 = (1 + r)^5

Taking the 5th root of both sides:

1+r=(1.57423875)151.0951 + r = \left(1.57423875\right)^{\frac{1}{5}} \approx 1.095

r0.095 or 9.5%r \approx 0.095 \text{ or } 9.5\%

Step 2: Find Compound Interest IcI_c

Ic=FP=12,593.918,000=4,593.91I_c = F - P = 12,593.91 - 8,000 = 4,593.91

Second Row:

Given:

  • Rate r=7.6%r = 7.6\% (or 0.076),
  • Time t=6t = 6 years,
  • Future Value F=23,279.03F = 23,279.03.

We need to find the Principal PP and Compound Interest IcI_c.

Step 3: Find Principal PP

Using the formula:

23,279.03=P(1+0.076)623,279.03 = P \left(1 + 0.076\right)^6

23,279.03=P(1.076)623,279.03 = P \left(1.076\right)^6

23,279.03=P×1.528923,279.03 = P \times 1.5289

P=23,279.031.528915,220P = \frac{23,279.03}{1.5289} \approx 15,220

Step 4: Find Compound Interest IcI_c

Ic=FP=23,279.0315,2208,059.03I_c = F - P = 23,279.03 - 15,220 \approx 8,059.03

Summary of the missing values:

  • Row 1: Rate r=9.5%r = 9.5\%, Compound Interest Ic=4,593.91I_c = 4,593.91,
  • Row 2: Principal P15,220P \approx 15,220, Compound Interest Ic8,059.03I_c \approx 8,059.03.

Would you like further clarification or details? Here are five questions you might consider:

  1. How is the compound interest formula adjusted for different compounding frequencies?
  2. What is the difference between simple and compound interest?
  3. How does the interest rate affect the growth of the principal over time?
  4. What happens if the interest is compounded monthly instead of annually?
  5. How can you solve for the principal if only the compound interest is known?

Tip: To solve for the rate rr, taking roots often requires logarithms if the time period isn't straightforward.

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Math Problem Analysis

Mathematical Concepts

Compound Interest
Algebra
Exponents

Formulas

Compound interest formula: F = P(1 + r/n)^(nt)
Compound interest calculation: I_c = F - P

Theorems

Compound interest growth theorem

Suitable Grade Level

Grades 10-12