The proportional relationship between inches and feet. Derive the equation of the line through the origin

first point (1, 12) second point (2, 24) third point (3, 36)

1 answer

Given a proportional relationship between inches and feet, we can express this relationship with a linear equation in the form:

\[ y = kx \]

where \( y \) represents the values in feet, \( x \) represents the values in inches, and \( k \) is a constant representing the proportionality factor.

Step 1: Determine the Proportionality Constant \( k \)

Using the first point (1, 12):

  • Here, \((x, y) = (1, 12)\)

Substituting into the equation:

\[ 12 = k(1) \]

Thus,

\[ k = 12 \]

We can check this constant with the other points.

Step 2: Check the other points

For the second point (2, 24):

  • \((x, y) = (2, 24)\)

Substituting into the equation:

\[ 24 = k(2) \]

Substituting \( k = 12 \):

\[ 24 = 12(2) \]

This holds true.

For the third point (3, 36):

  • \((x, y) = (3, 36)\)

Substituting into the equation:

\[ 36 = k(3) \]

Again substituting \( k = 12 \):

\[ 36 = 12(3) \]

This also holds true.

Step 3: Write the equation of the line

Since we have confirmed that the constant \( k \) is consistent across all points, we can write the equation of the line that represents the relationship between inches and feet as:

\[ y = 12x \]

This equation indicates that for every inch, there are 12 inches in a foot. This is a linear equation with a slope of 12, going through the origin (0, 0).