Walk the Plank
6th to 8th,High School
Samuel E. Zordak
To prepare for this lesson, draw a line on a sturdy plank of wood that
is 6 inches from one end. Then, draw additional lines at
12‑inch intervals. During the activity, students will stand with their
feet straddling these lines.
Place a bathroom scale and a textbook on the floor, about six feet
apart. Place the plank of wood so that one end rests firmly on the
scale and the other end rests on the book. The line drawn 6 inches from
one end of the plank should lie along the center of the scale. (Be sure
to test the arrangement prior to class to ensure that it is safe for
Provide the following explanation to students about the forthcoming
math investigation. (Since the lesson is called "Walk the Plank," it
may be fun to invoke a pirate accent while reading.)
Belay your talk, lads and lasses! Yo ho ho… ye all
have performed handsomely as math students, but I’m afraid there are
just too many of you in this here classroom. So today, some of ye are
going to walk the plank! (Point to the plank.) Aye, mateys! This here plank stretches between a scale and a textbook. Don’t ye be scared — it’s plenty sturdy. See? (Demonstrate its strength by walking across the plank.) As ye walk across it, we’ll record the weight shown on the scale. To show ye scallywags how to do it properly, I’ll go first.
(Point to the plank.) Aye, mateys! This here plank stretches between a scale and a textbook. Don’t ye be scared — it’s plenty sturdy. See? (Demonstrate its strength by walking across the plank.) As ye walk across it, we’ll record the weight shown on the scale. To show ye scallywags how to do it properly, I’ll go first.
Distribute the Walk the Plank Activity Sheet to students, and explain how the chart is to be filled in.
Walk the Plank Activity Sheet
Step on the plank so that your feet straddle the line down the
center of the scale. Read aloud the weight shown on the scale. (The
weight shown will be significantly more than your actual weight,
because it includes the weight of the plank.) On the chalkboard or
overhead projector, make a note of the weight.
Ask the class, "Do you think this is my actual weight?"
Students should realize that the weight shown on the scale includes the
weight of the plank. (Although it may seem trivial, this is an
important question to ask. When students realize that their actual
weight will not be displayed, they will be more likely to participate.
Still, when students walk the plank, use care with those who are
particularly self conscious.) Step off the plank.
Start at the line nearest the scale. Use the chart on the
activity sheet to record the weight. Step left, and move to the next
line on the plank. Again, read and record the weight. Continue moving
to the left and recording the weight at each line. If it becomes
difficult to read the weight, invite a student to read the weight as
you move across the plank. As you move and say the weight aloud, remind
students to fill in their charts.
After you have moved the entire way along the plank, ask the following questions:
Then, allow student(s) to walk the plank. If possible, select a
student whose weight is approximately half of your own weight. When the
line for this student is graphed, the slope of the line will be half of
the slope for your line. Then, select several other students at random.
(Because weight is a sensitive subject, choose students carefully, and
do not force any student to participate. To avoid an awkward situation,
you may want to ask for volunteers rather than select students.)
Allow students to discuss the questions on the activity sheet.
To fill the time and extend the thinking of those groups who finish the
worksheet and are waiting for others to finish, use the extension
The activity sheet can be reviewed after all groups have
discussed the question, or you may have students complete it for
If necessary, you can refer to the Walk the Plank Answer Key.
Walk the Plank Answer Key
Observe student answers during the class discussion, and check their written answers on the activity sheet.
Questions for Students
1. Why is the slope of the graph negative?
[As the person moved away from the scale, the weight displayed on the scale decreased.]
2. Why does the weight shown on the scale not accurately reflect your weight?
[The weight shown will be significantly more than your actual weight, because it includes the weight of the plank.]
3. When a student whose weight was about half of the teacher's walked across the plank, what did you notice about the slope of that student's line on the graph?
[The slope of the line was about half of the teacher's line.]
6th to 8th
9th to 12th
3rd to 5th