Calculating Areas of Rectangles

Ms. Ramon’s third grade class has been learning multiplication facts and how to use them to solve problems. Today they are working on finding the size of a two-dimensional flat surface. Ms. Ramon begins with several hands-on activities that are easy for them to visualize and remember. First, she marks off squares and rectangles on the floor with tape and has the children arrange 1 foot (or 1 meter) carpet squares inside the space and count the number of squares to come up with a measurement. The students compare the number of squares that fit inside smaller and larger shapes. Next, she gives each student a piece of paper with a square or rectangle marked off on it. She also gives them a bag of square crackers and they repeat the carpet activity. They label the size of each shape as number of square crackers or number square feet (or meters).

Next Ms. Ramon uses her laptop and a projector to show the students how to do a similar activity on the computer. Using Cacoo, a collaborative diagramming tool, she draws a large rectangle on the screen and drags enough squares on top of the rectangle to fill it. There are 2 rows of 3 squares. The students then count the squares and label the area of this as 6 square Cacoos, an invented unit of measurement. She then uses the group function to connect the 3 squares in a row so that they can be moved as a unit. They then discuss that the rows are equal and that 2 rows of 3 squares equals 6. She then shows them several ways to write this as a formula 3 + 3 = 6 or 3 x 2 = 6. She shows them that if they know the number of squares in a row and the number of rows, they can calculate the area without filling in all the squares. Finally, she has the students work in pairs using Cacoo, each on their own laptop. One student draws a rectangle on the screen and the other drags squares into the rectangle and either counts, adds, or multiplies to calculate the area.

.

Tools used in this scenario:
Visualization: Cacoo http://cacoo.com/
Virtual collaboration: Cacoo http://cacoo.com/
Simulation: Multiplication manipulative HERE

Last modified: Tuesday, May 29, 2012, 2:40 PM