Group Activity Cards
Use groups of 2.
Materials: Dot paper, scissors
Certain numbers can be represented with a picture. For instance, 3 and 6 are called triangular numbers because you can make a triangle with 3 and 6 points. Similarly, because you can make a square with 4 or 9 points, these numbers are called square numbers. Square numbers are perfect squares.
Every square number is the sum of two consecutive triangular numbers. In the figure below, 16 is shown to be the sum of 6 and 10.
Working together, model the square numbers 64, 169, 324, and 400 by cutting out sections of dot paper. Then draw a diagonal line to show that each of these numbers is the sum of two consecutive triangular numbers.