Lesson 3
Completion requirements
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1. Lesson 3
1.6. Explore 2
Module 1: Sequences and Series
Try This 2
Retrieve the strategy you developed in Share 1 to find the number of people in n levels of a pyramid. How is this question similar to the problem posed to young Gauss? In Try This 2 you will see how Gauss saw the problem and how you can develop a way to solve similar problems.
Step 1: Print a copy of Human Pyramid.
Step 2: Use scissors to cut a triangle around each pyramid. Be sure to cut as close to the figures as you can without cutting off an arm or a head!

Step 3: Arrange the two pyramids (or triangles) into the shape of a parallelogram so that all figures are visible. Not sure what a parallelogram is? Search the Internet for an image of a parallelogram.
- How many people are in each row of the parallelogram?
- How many rows are there in the parallelogram?
- Use your answers from questions 1 and 2 to determine the number of people in one pyramid.
- Use this new method to calculate the number of people required for a 100-row pyramid. Compare this answer to the one you calculated in Share 1.

Did you find that there are 5050 people in a 100-level pyramid? If so, your understanding has a strong base!