Finding Slope from Two Points

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Mathematics · Algebra I
SP-ALG1-005 · Free to print and use in your classroom · substituteplans.com
Page 2
Finding Slope from Two Points
Mathematics · Algebra I · Grades 8-9 · 50 minutes
Time needed
50 minutes (one class period)
Prep
Copy the 2-page worksheet (one per student). Write the slope formula and the worked
example on the board.
Technology
None. Calculators are optional for arithmetic only.
Student
independence
High. Students work alone, then compare with a partner.
Copies to make
One 2-page worksheet per student
Materials
Pencils, Worksheet, Whiteboard or chalkboard, Optional: graph paper or ruler
Goal for today: Students will calculate the slope of a line from two points using (y₂ − y₁)/(x₂ − x₁) and will interpret
slope as a rate of change.
Before the bell
☐ Copy the worksheet, one per student (2 pages).
☐ Write on the board: slope = rise ÷ run = (y₂ − y₁) ÷ (x₂ − x₁).
☐ Write the worked example on the board: points (1, 2) and (3, 8). Rise = 8 − 2 = 6. Run = 3 − 1 = 2. Slope =
6/2 = 3.
☐ Keep the answer key on your desk. You do not need to solve anything yourself.
Say this to start
Good morning! Today is about slope, which tells how steep a line is. Slope is the rise (how far up or down) divided by
the run (how far across). You will find the slope between pairs of points, think about what the answers mean, and
check a sample solution for a mistake. The formula and an example are on the board.

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Mathematics · Algebra I
SP-ALG1-005 · Free to print and use in your classroom · substituteplans.com
Page 3
Run of show
Minutes
What you do
What students do
0–5
Take attendance the way the school requires. Hand out the
worksheet face down and ask students to wait.
Settle in and take out a pencil.
5–13
Read the board example aloud. Say: “Subtract the y-values
to get the rise. Subtract the x-values in the SAME order to
get the run. Then divide.” Point out that a line going up
from left to right has a positive slope, and a line going
down has a negative slope.
Follow along and copy the formula and
example.
13–28
Tell students to complete Part A (problems 1–6). Walk the
room. If a student is stuck, ask, “Which point did you use
first? Did you subtract in the same order for x and y?”
Find the slope for each pair of points,
showing the rise and the run.
28–40
Tell students to complete Part B (questions 7–8), the table
and question 9, and the real-life problems 10–12. Partners
may check answers quietly.
Answer the questions and complete the
table.
40–46
Read the answers from the key. Students mark each right
or wrong and fix mistakes.
Check their work and correct errors in a
different color if possible.
46–50
Have students write the exit ticket sentence, then collect
all worksheets and stack them for the teacher.
Write one sentence. Hand in the worksheet.
If things go wrong
• If students get the sign wrong, tell them to subtract in the same order for both the y-values and the x-values.
• If a student asks about problem 5 (same x-value), explain that the run is 0 and you cannot divide by 0, so the
slope is undefined.
• If a student gets stuck on the table, tell them to find how much y changes each time x goes up by 1.
• If the class is noisy, remind them this is individual practice time. Partners may whisper during Part B.
Early finishers
• Choose two points of your own that give a slope of −2. Show the rise and run.
• Draw a quick sketch of lines with positive, negative, zero and undefined slope and label each.
Support and challenge
• Support: Let students sketch the two points on scrap paper and count rise and run. Have them complete
problems 1, 2, 3 and 6.
• Challenge: Ask students to find the value of k so that the slope between (1, 2) and (4, k) is 5.

SubstitutePlans.com
Mathematics · Algebra I
SP-ALG1-005 · Free to print and use in your classroom · substituteplans.com
Page 4
Notes for the teacher (you fill this in)
Jot a few lines before you leave. A full Daily Sub Report is in the free Sub Survival Kit at SubstitutePlans.com.
How far the class got / what to pick up next:
Students who were especially helpful:
Anything the teacher should know: