Walking
the Plank: Teacher Notes
MA.8.S.3.1
MA.912.A.3.11
Conceptual Understanding
Data Collection
Graphing Calculators
Interpret Data
Procedural Knowledge
y = mx + b
Graphing Linear Equations
Make Predictions
Problem Solving
Reasoning
Communication
Connections
Representation
Ever thought you could
lose weight by the foot, not the pound?
Students work as a whole
class
 1 bathroom scale
 2 textbooks
 1 2’ X 8’ plank
 Collect the Data:
Mark the 2’ x 8’ plank into one foot increments
Place the plank on the bathroom scale and textbooks as shown below:
Place graphic here (a bathroom scale on one side, 2
stacked books on the other side. The plank is laid so that one end
is lying on the scale and the other end is on the books. Line up the
ends of the plank with the sides of the scale and the sides of the
books.)
Weigh a volunteer person at each of the designated locations on the
plank.
Independent
Variable, X
Distance from Scale
(Feet)

Dependent Variable, Y
Weight
(Pounds)

0


1


2


3


4


5


6


 Graph the Data
Use "Distance from Scale (Feet)" as the horizontal scale
and "Weight (Pounds)" as the vertical scale. Plot ordered
pairs (X,Y).
 Read the Results
Looking at your graphed points, do they appear to lie along a straight
line or curve? Draw the line that best fits your data. Use the graph
to answer the following:
 Find the weight reading for the distances from the scale.
3.5 feet, _____ pounds
5.25 feet, _____ pounds
7 feet, _____ pounds
 How much does the weight reading decrease each time the person
moves another foot away from the scale?
____________________________________________________________________________________
How can you tell this from the graph? ____________________________________________________________________________________
 What is the person’s weight when standing directly on the
scale?
____________________________________________________________________________________
How can you tell this from the graph? ____________________________________________________________________________________
 Describe in words how to determine the weight reading if you know
how many feet the person is from the scale.
 Use your description to predict the weight reading for the person
when standing 4.75 feet from the scale. Show your work.
 Describe by equation how to determine the weight reading (Y) if
you know how many feet away (X) the person is from the scale:
Y= ____________________
 Use your equation to predict the weight reading for the person when
standing 6.5 feet away from the scale.
As a result of this activity,
students will learn how to collect, graph and interpret data.
