## Handshakes

3-5, 6-8
Standards:
Math Content:
Data Analysis and Probability

When the nine justices of the Supreme Court meet, they greet one another with a handshake to show harmony of purpose, even though their views may differ. How many handshakes occur? In general, how many handshakes occur when there are n people?

### How to Use

• Use the red points (people) to enlarge or decrease the size of the display.
• By highlighting two or more points, the location of the display can be moved.

### Buttons

The buttons are meant to be used sequentially.

• All the green buttons will show:
• The number of handshakes between the specified number of people.
• A diagram that shows how the handshakes are shared.

• The gray buttons will toggle on and off to show or hide values and/or segments.
• Use the Reset button to start over.

• What patterns do you notice between the number of people and the number of handshakes shared?
• If possible, what is a general formula showing the number of handshakes shared between n people? Assume that everyone shakes each other’s hand.