Math worksheet on writing trend line equations using scatter plots and slope-intercept form.

Let’s solve each part of the problem step by step.

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Problem 4a: Write the trend line equation. Specify what each variable represents.

We’re told the scatter plot shows:
- x-axis = number of items in a load of laundry
- y-axis = number of minutes it takes to fold the laundry

Looking at the graph, we can pick two points on the trend line to find the slope.

From the graph (and confirmed by the answer key), the trend line passes through:
- Point 1: (0, 0) → when there are 0 items, it takes 0 minutes
- Point 2: (10, 5) → 10 items take 5 minutes

Slope (m) = rise / run = (change in y) / (change in x) = (5 - 0) / (10 - 0) = 5/10 = 0.5

Since the line goes through (0,0), the y-intercept (b) is 0.

So the equation is:
y = 0.5x

Now define variables:
- x = number of items in the load of laundry
- y = number of minutes to fold the laundry

✔ This matches the given answer.

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Problem 4b: Use the equation to predict time for 60 items.

Equation: y = 0.5x
Plug in x = 60:

y = 0.5 × 60 = 30

So, it would take 30 minutes.

✔ Matches given answer.

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Problem 4c: Joey took 22 minutes — how many items?

Equation: y = 0.5x
We know y = 22, so solve for x:

22 = 0.5x
Divide both sides by 0.5:

x = 22 ÷ 0.5 = 44

So, Joey folded 44 items.

✔ Matches given answer.

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Final Answer:
a. Equation: y = 0.5x; x = number of items, y = minutes to fold
b. 30 minutes
c. 44 items