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 represent the number of weeks she makes withdrawals.
The inequality is:
Step 2: Solve the Equation to Find the Boundary
We need to solve the equation to determine the maximum number of weeks she can make withdrawals.
- Subtract 65 from 200:
- Divide by 15:
So, the boundary value is . 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
Now let’s plug in values below, at, and above the boundary to see if the inequality holds.
x | Expression | Result | Inequality True/False |
---|---|---|---|
8 | True | ||
9 | True | ||
10 | False |
Step 4: Write the Solution to the Inequality
From the truth table, we see that:
- The inequality is True when and .
- The inequality becomes False when .
Thus, the solution to the inequality is:
Step 5: Interpret the Meaning of
What does 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:
- What would the inequality look like if Chelsea started with $300 instead?
- How would the solution change if the minimum balance needed was $100?
- If Chelsea deposits $10 each week instead of withdrawing, what would the new inequality be?
- How many weeks would it take for Chelsea's account to be empty if she continues withdrawing $15 each week?
- 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
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