Threads Garage is a thrift store that sells clothing by the pound. Customers fill a plastic bag with their desired amount of clothing. Then, the bag is then weighed at checkout to calculate the cost.

There is a linear relationship between the weight of a bag of clothing, in pounds, and its cost.

Weight (pounds)

Cost

3

$9.00

6

$15.00

9

$21.00

12

$27.00

Describe the rate of change for this relationship.

The cost of a bag of clothing

per pound.

1 answer

To find the rate of change for the cost of a bag of clothing per pound, we can analyze the data provided. We see that as the weight increases, the cost increases linearly.

From the given data points:

  • For 3 pounds, the cost is $9.00.
  • For 6 pounds, the cost is $15.00.
  • For 9 pounds, the cost is $21.00.
  • For 12 pounds, the cost is $27.00.

We can calculate the cost per pound:

  1. For the first data point:

    • \( \frac{9.00}{3} = 3.00 \) : This means the cost is $3.00 per pound.
  2. For the second data point:

    • \( \frac{15.00}{6} = 2.50 \) : This means the cost is also $2.50 per pound.
  3. For the third data point:

    • \( \frac{21.00}{9} = 2.33 \) : This means the cost is approximately $2.33 per pound.
  4. For the fourth data point:

    • \( \frac{27.00}{12} = 2.25 \) : This means the cost is approximately $2.25 per pound.

Now we can observe the consistent price per pound across all weights:

Using the first data pair (3 pounds and $9.00) allows us to establish that the cost increases by $3 for each additional pound (since $9 for 3 pounds leads to a linear relationship where each additional pound costs $3). So, the cost per pound is:

\[ \text{Cost per pound} = \frac{Cost}{Weight} = \frac{$3.00}{1 \text{ pound}} \]

Therefore, the rate of change for this relationship is:

The cost of a bag of clothing is $3.00 per pound.