Math Problem Statement

Patrick spent last summer working in construction with his dad, and he put $894 of his earnings into a new high-yield savings account. The money in this savings account will increase by 2% each year. Write an exponential equation in the form y = a(b)^x that can model the amount of money in Patrick's account, y, x years after starting the account. If Patrick makes no other deposits or withdrawals, after how many years will his account have more than $1,000?

Solution

To solve this problem, let's break it down step by step:

1. Writing the Exponential Equation:

The general form of an exponential growth equation is: y=a(b)xy = a(b)^x where:

  • aa is the initial amount,
  • bb is the growth factor (rate of increase),
  • xx is the number of years,
  • yy is the amount of money in the account after xx years.

Given:

  • Patrick's initial deposit is a=894a = 894 dollars.
  • The account grows by 2% per year. This means the growth factor b=1+0.02=1.02b = 1 + 0.02 = 1.02.

Thus, the equation becomes: y=894(1.02)xy = 894(1.02)^x This is the exponential equation that models the amount of money in Patrick's account.

2. Finding When the Account Exceeds $1,000:

We need to find out after how many years xx the account will have more than $1,000. This means we want to solve the equation: 1000=894(1.02)x1000 = 894(1.02)^x

To solve for xx: 1000894=(1.02)x\frac{1000}{894} = (1.02)^x 1.1189=(1.02)x1.1189 = (1.02)^x

Now, take the natural logarithm (ln) of both sides: ln(1.1189)=xln(1.02)\ln(1.1189) = x \ln(1.02) x=ln(1.1189)ln(1.02)x = \frac{\ln(1.1189)}{\ln(1.02)} Using a calculator: x0.112410.019805.68x \approx \frac{0.11241}{0.01980} \approx 5.68

So, Patrick's account will have more than $1,000 after about 6 years.


Do you have any questions or would you like more details? Here are some related questions to extend your understanding:

  1. What would the balance be after 10 years?
  2. How would the equation change if the interest rate was 3% instead of 2%?
  3. How does exponential growth differ from simple interest growth?
  4. Can you graph the function y=894(1.02)xy = 894(1.02)^x to visualize the growth?
  5. What happens if Patrick adds more deposits each year? How would that affect the equation?

Tip: When solving exponential equations, using logarithms is a powerful tool for isolating the exponent.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Exponential Growth
Algebra

Formulas

Exponential equation: y = a(b)^x
Logarithms

Theorems

Exponential growth model
Logarithm to solve for exponent

Suitable Grade Level

Grades 9-12