E2.5Use the row and column structure of an array to measure the areas of rectangles and to show that the area of any rectangle can be found by multiplying its side lengths.
Activity 1: Finding the Area of the a Rectangle including a Square
Goal
In this activity students develops an understanding of the area of the rectangle and the area of the square through a row and column structure.
Material
- Appendix 1(cardboard rectangles of various sizes)
- Appendix 4 (centimetre square grid on an overhead transparency)
- graph paper and pencil
- rulers graduated in centimetres
- square tiles and small cubes from base 10 materials or a set of Cuisenaire® rods
Instructions
Form teams of two students.
Give each team two different cardboard rectangles.
Have students measure the area of the rectangle using the strategy and materials of their choice.
Ask some teams to share the strategy they used to determine the area of the rectangle.
Emphasize the unit used to measure the area of the rectangle.
Ask the following questions:
- How many squares are on the length of your rectangle?
- How many squares are in the width of your rectangle?
- What are the dimensions of your rectangle?
- What unit did you use to measure the area of your rectangle?
- How many units completely cover your rectangle?
- What is the area of its surface?
- What is the relationship between the amount of units for the length and width of your rectangle and the measurement of its area?
- How would you write the calculation of the area of your rectangle?
Note: At this point, on the row and column structure of an array to measure. For example, “My rectangle had 4 squares in a column (or rows) and there were 3 columns” or “My rectangle was 4 squares by 3 squares.”
Without showing students a rectangle, ask the following questions:
- What is the area of a 7 cm by 8 cm rectangle?
- What is the area of a rectangle of … cm by…cm?
Concepts the Student Should Understand upon Completion of This Activity
- the area of rectangle or a square can be found by multiplying the lengths of their sides
Source: translated from L’@telier - Ressources pédagogiques en ligne (atelier.on.ca).