Making Connections:

Pascal's Triangle and the Sierpinski Triangle Fractal

Curriculum Topics:Pascal's triangle, binomial coefficients, patterns of even and odd numbers
Fractal Topics:Sierpinski triangle, generating fractals by recursion
Number of Days:1
Grades:
PreCalculus Course (high school or college level)
Pre-Service or In-Service Mathematics Teachers Course (college level)
Liberal Arts Mathematics Course (college level)
Authors:
Virginia R. JonesCentral Connecticut State University
Kathleen Stankewicz
Objective:To have the students compare the Pascal Triangle to the Sierpinski Triangle and discover relationships and patterns that occur within each mathematical object and between the two mathematical objects.
Resources:
Working from handouts of:
1) an equilateral "grid" for displaying the Pascal Triangle which requires the students to fill in the first 16 rows of numbers in the Pascal triangle. (This gives the opportunity to review the coefficients of the binomial expansion for (x + y)n and to discuss the symmetry about the center of Pascal's triangle.)
2) a display of the Sierpinski Triangle for the first four levels
Note: These handouts can be simple paper copies or transparency overlays. Click for copies of Pascal's triangle and the Sierpinski triangle in new windows.
Description of Lesson:
Activities: (not an exhaustive list)
After the students have entered the values in the Pascal Triangle, have them highlight the values that are even numbers.
1) Ask them to describe what happens when they place the Sierpinski Triangle over the Pascal Triangle and align the two objects.
2) Ask them to conjecture what would happen if both the grids were extended so the Pascal Triangle had more rows below the given grid and the Sierpinski Triangle was extended so it covered the new Pascal grid.
3) Have them shift the Sierpinski Triangle so that the triangle of it matches a value in some other row of the Pascal Triangle grid. Can they see another relationship between the two objects? Can they write a conjecture about this relationship in mathematical terms?

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