• ### C.1. Counting Figures

3. #### C.1.1. Counting Line Segments, Angles, and Handshakes

1. C.1.1.O. Overview
2. C.1.1.1. Counting Basic Line Segments
3. C.1.1.2. Counting Line Segments in Pictures
4. C.1.1.3. Counting Angles
5. C.1.1.4. Counting Handshakes
4. #### C.1.2. Counting Squares, Rectangles, and Triangles

1. C.1.2.O. Overview
2. C.1.2.1. Counting Rectangles
3. C.1.2.2. Counting Squares
4. C.1.2.3. Counting Triangles
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• ### C.2. Unexpected Counting

3. #### C.2.1. Clocks, Stairs, and Wood

1. C.2.1.O. Overview
2. C.2.1.1. Climbing Stairs
3. C.2.1.2. Sawing Wood
4. C.2.1.3. Striking Grandfather Clocks
4. #### C.2.2. Planting Trees and Grids

1. C.2.2.O. Overview
2. C.2.2.1. Planting Trees in Straight Lines
3. C.2.2.2. Planting Trees in Loops
4. C.2.2.3. Standing in Grids
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• ### C.3. Pigeonhole

3. #### C.3.1. Introduction to the Pigeonhole Principle

1. C.3.1.O. Overview
2. C.3.1.1. Filling Holes
3. C.3.1.2. Counting Pigeons
4. C.3.1.3. Lots of Pigeons
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• ### C.4. PIE & Venn Diagrams

3. #### C.4.1. Two Overlapping Sets with Venn Diagrams

1. C.4.1.O. Overview
3. C.4.1.2. Use Venn diagrams to Solve problems
4. C.4.1.3. More Practice with Venn Diagrams
4. #### C.4.2. Three or More Sets

1. C.4.2.O. Overview
2. C.4.2.1. Three or more sets: Intro
3. C.4.2.2. Three or more sets: Medium
4. C.4.2.3. Three or more sets: Advanced
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• ### C.5. Standard Counting

3. #### C.5.1. Counting by Multiplication

1. C.5.1.O. Overview
2. C.5.1.1. Counting by Multiplication I
3. C.5.1.2. Restrictions on Multiplication
4. #### C.5.2. Combinations: when order doesn't matter

1. C.5.2.O. Overview
2. C.5.2.1. Combinations: when order DOESN’T matter
3. C.5.2.2. The Mississippi Trick
5. #### C.5.3. Counting by Subtraction, Patterns, Listing, Putting Everything Together

1. C.5.3.O. Overview
2. C.5.3.1. Counting with Patterns
3. C.5.3.2. Counting by Subtraction
4. C.5.3.3. Counting by Listing
5. C.5.3.4. Putting Everything Together
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