Write an equation to represent the total cost of a repair, y, as a function of the number of hours spent fixing a leak, x.

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Understand the Problem

The question is asking to formulate an equation that represents the total cost of a repair, expressed as a function of the number of hours spent on the repair. We need to identify the structure of the costs involved based on the given information about costs for different hours.

Answer

The equation for total cost is $y = 20 + 40x$.
Answer for screen readers

The equation representing the total cost of a repair is: $$ y = 20 + 40x $$

Steps to Solve

  1. Identify the costs involved

From the problem, we know two costs:

  • For 2 hours, the cost is $100: $$ y = c + 2h $$
  • For 6 hours, the cost is $260: $$ y = c + 6h $$

Where $c$ is the travel fee and $h$ is the hourly fee.

  1. Create a system of equations

We can set up two equations based on the information provided:

  • For 2 hours: $$ 100 = c + 2h $$
  • For 6 hours: $$ 260 = c + 6h $$
  1. Solve the system of equations

Subtract the first equation from the second to eliminate $c$:

$$ (260 - 100) = (c + 6h) - (c + 2h) $$

This simplifies to:

$$ 160 = 4h $$

Now, solve for $h$:

$$ h = \frac{160}{4} = 40 $$

  1. Substitute back to find ( c )

Now, substitute $h = 40$ back into the first equation:

$$ 100 = c + 2(40) $$

Calculate:

$$ 100 = c + 80 $$

Thus,

$$ c = 100 - 80 = 20 $$

  1. Formulate the total cost equation

Now that we have $c$ and $h$, we can express the total cost $y$ as:

$$ y = c + hx $$ Substituting the values of $c$ and $h$, we get: $$ y = 20 + 40x $$

The equation representing the total cost of a repair is: $$ y = 20 + 40x $$

More Information

In this equation, $y$ is the total cost, $x$ is the number of hours spent fixing the leak, $20 is the travel fee, and $40 is the hourly rate. This formulation helps in predicting costs for any number of hours worked.

Tips

  • Mistaking fixed costs for variable costs: Sometimes, learners confuse the travel fee (fixed) with the hourly fee (variable). Keep these separate.
  • Forgetting to define variables clearly: Ensure that you label what each variable represents to avoid confusion.

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