Math Problem Statement

Suppose that a new employee starts working at $7.16 per hour and receives a 5% raise each year. After time t, in years, his hourly wage is given by the equation y = $7.16(1.05)^t. Find the amount of time after which he will be earning $10.00 per hour.

Solution

The problem describes a scenario where an employee’s hourly wage increases by 5% each year. The wage is represented by the equation:

y=7.16(1.05)ty = 7.16 \cdot (1.05)^t

where tt is the time in years, and the goal is to determine how long it will take for the wage to reach $10.00 per hour.

Solution:

We need to solve for tt when y=10.00y = 10.00:

10=7.16(1.05)t10 = 7.16 \cdot (1.05)^t

  1. Divide both sides by 7.16 to isolate the exponential term: 107.16=(1.05)t\frac{10}{7.16} = (1.05)^t 1.396=(1.05)t1.396 = (1.05)^t

  2. Take the natural logarithm (ln) of both sides: ln(1.396)=ln((1.05)t)\ln(1.396) = \ln((1.05)^t)

  3. Apply the logarithmic property ln(ab)=bln(a)\ln(a^b) = b \ln(a): ln(1.396)=tln(1.05)\ln(1.396) = t \cdot \ln(1.05)

  4. Solve for tt: t=ln(1.396)ln(1.05)t = \frac{\ln(1.396)}{\ln(1.05)}

Using a calculator: ln(1.396)0.3328andln(1.05)0.04879\ln(1.396) \approx 0.3328 \quad \text{and} \quad \ln(1.05) \approx 0.04879 t=0.33280.048796.82t = \frac{0.3328}{0.04879} \approx 6.82

Final Answer:

The employee will be earning $10.00 per hour after approximately 6.8 years (rounded to the nearest tenth).

Let me know if you would like a detailed breakdown or have additional questions! Here are related questions to explore:

  1. What happens if the annual raise is increased to 7%?
  2. How would the formula change if the starting wage was $8.00?
  3. What is the employee's wage after 10 years?
  4. How can we use this formula to calculate yearly wages for other jobs?
  5. How does compounding affect other forms of growth, such as savings?

Tip: Always check for correct rounding when working with real-world applications!

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Math Problem Analysis

Mathematical Concepts

Exponential Growth
Logarithms
Algebra

Formulas

y = y0 * (1 + r)^t
t = ln(y / y0) / ln(1 + r)

Theorems

Properties of Logarithms

Suitable Grade Level

Grades 9-12