## Slope

Slope refers to the Steepness of a Line

Basics

Slope refers to the steepness of a line.
Line 1 is steeper than Line 2.
Line 1’s slope is greater than Line 2’s slope.

A line is a flat straight figure extending infinitely through two points.  (See Line L above.)
x-axis = horizontal
y-axis = vertical
x = horizontal coordinate
y = vertical coordinate
(x, y) = point representing horizontal and vertical coordinates on Line L
(o, b) = y-intercept = point where Line L crosses the y-axis
m = slope

Formulas (provided by Formula Sheet)
slope of a line
$\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$

Formulas (NOT provided by Formula Sheet)
slope as change
$\bf\displaystyle m=\frac{{{change\;in\;y}}}{{{change\;in\;x}}}$

Question
What is the slope of Line 1?

m = 2

slope as change
$\bf\displaystyle m=\frac{{{change\;in\;y}}}{{{change\;in\;x}}}$

$\displaystyle\text{m = }\frac{1\text{0 boxes up positive y-axis}}{\text{5 boxes along positive x-axis}}$$\bf\displaystyle\frac{10}{5}$ = 2

Question
What is the slope of Line 2?

m = $\bf\displaystyle\frac{1}{2}$

slope as change
$\bf\displaystyle m=\frac{{{change\;in\;y}}}{{{change\;in\;x}}}$

$\displaystyle\text{m = }\frac{\text{5 boxes up positive y-axis}}{\text{10 boxes along positive x-axis}}$$\bf\displaystyle\frac{5}{10}$$\bf\displaystyle\frac{1}{2}$

Question

Using the points (3, 1) and (8, 3) in the graph below, calculate the slope of line L.

m = $\bf\displaystyle\frac{2}{5}$

(x1, y1) = (3, 1)
(x2, y2) = (8, 3)

slope of a line
$\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$

$\bf\displaystyle m =\frac{3-1}{8-3}$$\bf\displaystyle\frac{2}{5}$

Calculator Click What You See Comment
3 – 1  8 – 3   $\bf\displaystyle m =\frac{3-1}{8-3}$ $\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$
$\bf\displaystyle\frac{2}{5}$ Answer
###### Slope

Question
Express the previous answer in decimal form.

m = 0.4

See Toggle.
$\bf\displaystyle\frac{2}{5}$ ⇔ 0.4

Calculator Click What You See Comment
3 – 1  8 – 3   $\bf\displaystyle m =\frac{3-1}{8-3}$ $\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$
$\bf\displaystyle\frac{2}{5}$
(Toggle)
###### Slope

Question
Using the points (1, 2) and (4, 9) in the graph below, calculate the slope of line L in decimal form.

m = 2.333333333

(x1, y1) = (1, 2)
(x2, y2) = (4, 9)

slope of a line
$\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$

$\bf\displaystyle m =\frac{9-2}{4-1}$$\bf\displaystyle\frac{7}{3}$ = 2.333333333 after toggle

Calculator Click What You See Comment
9 – 2  4 – 1   $\bf\displaystyle m =\frac{9-2}{4-1}$ $\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$
$\bf\displaystyle\frac{7}{3}$
(Toggle)
###### Slope

Question
Round the previous answer to the nearest tenth.

m = 2.3

See Rounding.
2.333333333  2.3

Question
On the graph below, plot the points (2, 3) and (6, 9), draw a line through them, and calculate the slope of the line in decimal form.

m = 1.5

(x1, y1) = (2, 3)
(x2, y2)= (6, 9)

slope of a line
$\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$

$\bf\displaystyle m =\frac{9-3}{6-2}$$\bf\displaystyle\frac{3}{2}$ = 1.5 after toggle

Calculator Click What You See Comment
9 – 3  6 – 2   $\bf\displaystyle m =\frac{9-3}{6-2}$ $\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$
$\bf\displaystyle\frac{3}{2}$
(Toggle)
###### Slope

Question
On the graph below, plot the points (4, 1) and (10, 2) and calculate their slope in decimal form rounded to the nearest hundredth (without drawing a line).

m = 0.17

(x1, y1) = (4, 1)
(x2, y2) = (10, 2)

slope of a line
$\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$

$\bf\displaystyle m =\frac{2-1}{10-4}$$\bf\displaystyle\frac{1}{6}$0.166666667 after toggle = 0.17 after rounding

Calculator Click What You See Comment
2 – 1  10 – 4   $\bf\displaystyle m =\frac{2-1}{10-4}$ $\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$
$\bf\displaystyle\frac{1}{6}$
(before rounding)
###### Slope

Question
On the graph below, plot the points (3, 2.5) and (7, 6.25) and calculate their slope in decimal form to the nearest hundredth (without drawing a line).

m = 0.94

(x1, y1) = (3, 2.5)
(x2, y2) = (7, 6.25)

slope of a line
$\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$

$\bf\displaystyle m =\frac{6.25-2.5}{7-3}$0.9375 = 0.94 after rounding

Calculator Click What You See Comment
6.25 – 2.5  7 – 3   $\bf\displaystyle m =\frac{6.25-2.5}{7-3}$ $\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$
(before rounding)
###### Slope

Question
The following table shows the age in years and height in inches of a boy and a girl.

On the grid below the table, plot the x-y coordinates for the boy at ages 2 and 8 and calculate their slope in decimal form to the nearest tenth (without drawing a line).

 Boy Girl Age (yr) Height (in) Age (yr) Height (in) 2 34.00 2 33.50 3 37.50 3 37.00 4 40.00 4 39.50 5 43.00 5 42.25 6 45.25 6 45.00 7 48.00 7 48.00 8 50.25 8 50.00 9 52.50 9 52.50 10 54.50 10 54.25

m = 2.7

(x1, y1) = (2, 34.00)
(x2, y2) = (8, 50.25)

slope of a line
$\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$

$\bf\displaystyle m =\frac{50.25-34.00}{8-2}$ = 2.708333333 = 2.7 after rounding

Calculator Click What You See Comment
50.25 – 34.00  8 – 2   $\bf\displaystyle m =\frac{50.25-34.00}{8-2}$ $\bf\displaystyle m=\frac{{{y}_{2}}-{{y}_{1}}}{{{x}_{2}}-{{x}_{1}}}$
(before rounding)
###### Slope

Practice – Questions
1.  What is the slope of Line 1?

2.  What is the slope of Line 2?

3.  Using the points (3.5, 1.5) and (7, 3.25) in the graph below, calculate the slope of line L.

4.  On the graph below, plot the points (4, 1) and (8, 2), draw a line through them, and calculate the slope of the line in decimal form.

5.  On the graph below, plot the points (1, 4) and (2, 8) and calculate their slope (without drawing a line).

6.  The following table shows the age in years and height in inches of a boy and a girl.

On the grid below the table, plot the x-y coordinates for the girl at ages 3 and 9 and calculate their slope in decimal form (without drawing a line).

 Boy Girl Age (yr) Height (in) Age (yr) Height (in) 2 34.00 2 33.50 3 37.50 3 37.00 4 40.00 4 39.50 5 43.00 5 42.25 6 45.25 6 45.00 7 48.00 7 48.00 8 50.25 8 50.00 9 52.50 9 52.50 10 54.50 10 54.25

7.  With reference to Question 6, express your answer as a fraction.

8.  The following table shows the age in years and mileage for Car A and Car B.

On the grid below the table, plot the x-y coordinates for Car A at years 3 and 6 and calculate their slope (without drawing a line).

 Car A Car B Age Mileage Age Mileage 1 10000 1 11000 2 22000 2 20500 3 33500 3 29725 4 39000 4 41000 5 48000 5 50500 6 62000 6 58750 7 71000 7 69900 8 83250 8 81000 9 90500 9 89900 10 99500 10 99500

9.  The following table shows the age in years and mileage for Car A and Car B.

On the grid below the table, plot the x-y coordinates for Car B at years 2 and 9 and calculate their slope (without drawing a line).

 Car A Car B Age Mileage Age Mileage 1 10000 1 11000 2 22000 2 20500 3 33500 3 29725 4 39000 4 41000 5 48000 5 50500 6 62000 6 58750 7 71000 7 69900 8 83250 8 81000 9 90500 9 89900 10 99500 10 99500

10.  With reference to Question 9, round your answer to the nearest tenth.

1.  m = 1

2.  m = 2

3.  m = 0.5

4.  m = 0.25

5.  m = 4

6.  m = 2.583333333

7.  $\bf\displaystyle m =\frac{31}{12}$
See Toggle.

8.  m = 9500

9.  m = 9914.285714

10.  m = 9914.3