Math Problem Statement

Find the interest rate for aa ​$44000 deposit accumulating to ​$49734973​, compounded annually for 77 years. Question content area bottom Part 1 The interest rate is enter your response here​%. ​(Do not round until the final answer. Then round to two decimal places as​ needed.)

Solution

To solve for the annual interest rate rr for a principal P=44,000P = 44,000 to grow to an accumulated amount A=49,734,973A = 49,734,973 over t=77t = 77 years, compounded annually, we can use the compound interest formula:

A=P(1+r)tA = P(1 + r)^t

Step 1: Substitute the known values into the formula

49,734,973=44,000(1+r)7749,734,973 = 44,000(1 + r)^{77}

Step 2: Isolate (1+r)77(1 + r)^{77}

Divide both sides by 44,000:

49,734,97344,000=(1+r)77\frac{49,734,973}{44,000} = (1 + r)^{77}

1,130.34=(1+r)771,130.34 = (1 + r)^{77}

Step 3: Take the 77th root of both sides to solve for 1+r1 + r

1+r=(1130.34)1771 + r = (1130.34)^{\frac{1}{77}}

Step 4: Calculate the result

Using a calculator or computational tool, find the 77th root of 1130.34:

1+r1.1041 + r \approx 1.104

Step 5: Solve for rr by subtracting 1

r1.1041=0.104or10.4%r \approx 1.104 - 1 = 0.104 \quad \text{or} \quad 10.4\%

Final Answer

The interest rate is approximately 10.4%.

Would you like more detailed steps or have any other questions?


Here are 5 additional questions to explore this topic further:

  1. What happens to the accumulated amount if the interest rate is compounded monthly instead?
  2. How would the interest rate change if the time period was only 50 years?
  3. How does compound interest differ from simple interest in terms of growth over long periods?
  4. What if the principal amount was doubled; how would that affect the accumulated total?
  5. How sensitive is the accumulated amount to changes in the interest rate?

Tip: Always use the appropriate root (such as 1t\frac{1}{t}) when solving for the rate in compounded interest problems.

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Math Problem Analysis

Mathematical Concepts

Compound Interest
Exponential Growth
Logarithms

Formulas

Compound Interest Formula: A = P(1 + r)^t

Theorems

Exponentiation and Root Extraction

Suitable Grade Level

Grades 10-12