Math Problem Statement

Chelsea starts with $200 in her bank account. Every week she withdraws $15 for miscellaneous expenses. For how many weeks could she withdraw the money if she maintains a balance of at least $65? Write an inequality to represent the situation. Use x to represent the number of weeks. Good work! You just wrote an inequality to represent the situation. Now solve the associated equation, 200 - 15x = 65, to find the boundary for the inequality. Show your work or solve on paper. 200 - 15x ≥ 65 200−15x

65

x

Nice! Fill in the table to show whether a value below the boundary, the boundary, and a value above the boundary make the inequality true or false. x= 8 x=9 (boundary) x= 10 200 - 15x ≥ 65 Good work! Now use your table to help you write the solution to the inequality. x= 8 x=9 (boundary) x= 10 200 - 15x ≥ 65 True True False x

9 You got it! What does x≤ 9 mean in this problem?

Chelsea has been withdrawing money for exactly 9 weeks or less than 9 weeks.

Chelsea has been withdrawing money for less than 9 weeks.

Chelsea has less than $9 in her account.

Solution

Step 1: Write the Inequality

The problem states Chelsea starts with $200 and withdraws $15 every week, maintaining a balance of at least $65. Let xx represent the number of weeks she makes withdrawals.

The inequality is:
20015x65200 - 15x \geq 65


Step 2: Solve the Equation to Find the Boundary

We need to solve the equation 20015x=65200 - 15x = 65 to determine the maximum number of weeks she can make withdrawals.

  1. Subtract 65 from 200: 20065=135200 - 65 = 135
  2. Divide by 15: x=13515=9x = \frac{135}{15} = 9

So, the boundary value is x=9x = 9. This means Chelsea can withdraw money for exactly 9 weeks before the balance drops below $65.


Step 3: Fill in the Truth Table for Different Values of xx

Now let’s plug in values below, at, and above the boundary to see if the inequality 20015x65200 - 15x \geq 65 holds.

xExpressionResultInequality True/False
820015(8)=80200 - 15(8) = 80806580 \geq 65True
920015(9)=65200 - 15(9) = 65656565 \geq 65True
1020015(10)=50200 - 15(10) = 50506550 \geq 65False

Step 4: Write the Solution to the Inequality

From the truth table, we see that:

  • The inequality is True when x=8x = 8 and x=9x = 9.
  • The inequality becomes False when x=10x = 10.

Thus, the solution to the inequality is: x9x \leq 9


Step 5: Interpret the Meaning of x9x \leq 9

What does x9x \leq 9 mean in this problem?

  • Correct Answer: Chelsea has been withdrawing money for exactly 9 weeks or less than 9 weeks.

Let me know if you have any further questions!
Here are five related questions to deepen your understanding:

  1. What would the inequality look like if Chelsea started with $300 instead?
  2. How would the solution change if the minimum balance needed was $100?
  3. If Chelsea deposits $10 each week instead of withdrawing, what would the new inequality be?
  4. How many weeks would it take for Chelsea's account to be empty if she continues withdrawing $15 each week?
  5. What if the amount she withdraws each week increases to $20? How would that change the inequality?

Tip: When solving inequalities, always remember to carefully handle signs when dividing or multiplying by negative numbers!

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Math Problem Analysis

Mathematical Concepts

Algebra
Inequalities
Linear Equations

Formulas

200 - 15x ≥ 65

Theorems

Basic inequality solving

Suitable Grade Level

Grades 6-8