**Title:** Arithme-Tic-Toc

**Description:**
In this Illuminations lesson, students are introduced to modular arithmetic by first examining a five-hour analog clock and its mathematical properties. Then students investigate patterns and relationships that exist in 12-hour addition and multiplication clock tables. There are links to online activity sheets and other resources.

**Standard(s): **

[MA2013] AL2 (9-12) 3: (+) Find the conjugate of a complex number; use conjugates to find moduli and quotients of complex numbers. [N-CN3]

[MA2013] PRE (9-12) 3: (+) Calculate the distance between numbers in the complex plane as the modulus of the difference, and the midpoint of a segment as the average of the numbers at its endpoints. [N-CN6]