Explaining the commutative and distributive laws

Patterns: perimeter, area and dots

Problem types and difficulties

• intro
• Lots of details
• The practice quiz
• Difficulty notes and more resources

Scaffolding division

Bar diagrams

Alternate addition and subtraction algorithms

• Adding on in chunks using multiples of 10 and 100 as bridge numbers
• Add in place values and combine
• Adding up to the minuend in chunks using multiples of 10 (and 100) as bridge numbers
• Subtract in place values using negative numbers, the negative numbers algorithm

More about shapes

• the big menu
• the specific page for definitions of common shapes
• the specific page for definitions of geometric properties

Geoboard area

Direct Modeling

Venn diagrams with shapes

•  definitions of common shapes
•  definitions of geometric properties

Explaining the addition and subtraction algorithms

Making a parallelogram from two triangles

Drawing perpendiculars to show height of a triangle, and drawing parallels to make a parallelogram. Video. Practice. Answers

Word problems with Venn diagrams

Scaffolding division