Wednesday 2:00 PM - 3:15 PM (in-person or virtually)

Tuesday and Thursday 3:00 PM - 4:15 PM (virtually)

## Biography

My name is Gabriel Tarr. I am faculty at Scottsdale Community College (SCC). I have been teaching here at SCC since Fall 2016. I have been teaching in general since 2009 (depending on how one defines *teaching*). My academic interests lie in mathematics and statistics education, mathematics, and statistics (yes, they are related, but DISTINCT). I am currently a PhD candidate at Arizona State University studying how people understand statistical concepts.

In some of my spare time, I do fun logic/maths puzzles. Here are a couple of them that are pretty approachable regardless of mathematical ability. They just require a little thought.

- There are 1000 doors (initially closed) and 1000 students. The 1st student opens each door. The 2nd student changes every second door. The 2nd student closes the door if it is open and opens the door if it is closed. The 3rd student changes every third door. The 3rd student closes the door if it is open and opens the door if it is closed. This pattern continues until all 1000 students have changed their assigned doors. How many doors remain open? Which doors are they?

- (Easy) There are 9 coins. 8 of these coins are gold and the remaining coin is a fake gold coin that only differs from the others by weighing less than the other 8. You have a very precise balance that can compare the weights for two groups of coins. Using the balance only twice, determine which of the 9 coins is a fake. What is your strategy?
(Hard) There are 12 coins. 11 of these coins are gold and the remaining coin is a fake gold coin that only differs from the others by weight. The fake can weigh less or more, but you don’t know which. You have a very precise balance that can compare the weights for two groups of coins. Using the balance only thrice (three times), determine which of the 12 coins is a fake and if it weighs less or more than the real coins. What is your strategy?