Before lesson, draw two geometric shapes on two poster-sized
sheets of graph paper. Be
sure that the shape carefully follows the grid on the paper.
Explain to students that you are going to give them a geometric
challenge. Show the class
the first shape you have drawn, and tell them they are to copy it
exactly, but they are to use smaller graph paper.
Ask for some suggestions from the class for strategies they may
Give each student a sheet of graph paper, a pencil, and a
ruler, and have them copy the shape.
When every student is done, share the shapes as a class and
discuss their strategies.
Ideally, one or more students will have used a gridding
process. Have those students explain the process to the class.
If no one has done so, you can explain the process.
Point out to students that the grid boxes can be used as a
measuring tool. Where
your shape may have one side that is 6 boxes long, their copy should
have one side that is 6 boxes long.
If all of the sides match up in that way, the shape the student
has drawn will be an exact replica of your shape, drawn to scale.
Give each student another sheet of graph paper.
Show the class the second shape you have drawn on poster-sized
graph paper, and have students copy the shape again using the gridding
process you have explained. When
they are done, ask volunteers to share their shapes and explain how
they were made.
For additional practice, have half the class draw shapes on
poster-sized graph paper, then give each shape to the student in
the other half of the class to copy.
Share and discuss the shapes again.
Ask the class, "How can we relate this activity to map
making?" Elicit from
students that map makers have to use a similar process to scale down
large areas. Show the class a map which features longitude and latitude
lines. That is the grid
used by map makers, and they use the same process of "scaling
down" used by the class to draw their shapes.