Math Problem Statement

5500 dollars is placed in an account with an annual interest rate of 5.25%. To the nearest year, how long will it take for the account value to reach 11100 dollars?

Solution

We can solve this problem using the compound interest formula:

A=P(1+r)tA = P \left(1 + r\right)^t

Where:

  • AA is the future value of the investment ($11,100).
  • PP is the initial principal ($5,500).
  • rr is the annual interest rate (5.25% or 0.0525 as a decimal).
  • tt is the time in years.

Plugging in the values:

11100=5500(1+0.0525)t11100 = 5500 \left(1 + 0.0525\right)^t

First, divide both sides by 5500 to isolate the growth factor:

111005500=(1.0525)t\frac{11100}{5500} = \left(1.0525\right)^t

2.01818=(1.0525)t2.01818 = \left(1.0525\right)^t

Next, take the natural logarithm of both sides to solve for tt:

ln(2.01818)=tln(1.0525)\ln(2.01818) = t \cdot \ln(1.0525)

t=ln(2.01818)ln(1.0525)t = \frac{\ln(2.01818)}{\ln(1.0525)}

Now, calculate tt:

t0.701130.0511713.7t \approx \frac{0.70113}{0.05117} \approx 13.7

So, it will take approximately 14 years for the account value to reach $11,100.

Would you like more details or have any questions?


Here are 8 related questions:

  1. How would the time change if the interest rate were increased to 6%?
  2. What if the principal amount were $7,000 instead of $5,500?
  3. How long would it take to triple the initial investment at 5.25% interest?
  4. What would be the final amount after 14 years if the principal was $5,500 but the interest rate was 4%?
  5. How does the compounding frequency (monthly vs. annually) affect the time to double the investment?
  6. What would be the time to reach $15,000 with the same initial investment and interest rate?
  7. If you need the money in 10 years, what interest rate would be required to reach $11,100?
  8. How does the concept of present value relate to this calculation?

Tip: Keep in mind that small differences in interest rates can significantly affect the time required for an investment to grow, especially over longer periods.

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Math Problem Analysis

Mathematical Concepts

Compound Interest
Exponential Growth

Formulas

Compound Interest Formula

Theorems

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Suitable Grade Level

High School