In this math meets physics lesson, learners encounter the magical effect of reflection as they use a mirror to visually experience the concept of doubling quantities. This experience focuses learners' attention to using doubles as a strategy to make number operations easier, specifically addition. The book "Two of Everything" by Lily Toy Hong is used to introduce learners to these concepts. A game is used for discovery and practice and writing is used as closure to this lesson. This lesson guide includes questions for learners, assessment options, extensions, and reflection questions.

The four games that can be played with this applet help to develop counting and addition skills using frames of 10.

The words compose and decompose are used to describe actions that young students learn as they acquire knowledge of small numbers by putting them together and taking them apart. This understanding is a bridge between counting and knowing number combinations. It is how instant recognition of small numbers develops and leads naturally to later understanding of fact families. This task helps them develop an understanding of number combinations.