Compare and classify geometric shapes based on their properties and sizes; understand that attributes belonging to a category also belong to all subcategories; classify two-dimensional figures in a hierarchy based on properties
You already know how to describe shapes by their sides and angles. Now use those same properties to sort shapes into families. A shape can belong to more than one family at once: a big general family, and a smaller, more exact family inside it.
A rectangle needs 4 right angles and opposite sides equal. A square has 4 right angles and all 4 sides equal, so it passes every rectangle test too. That is why every square is a rectangle. But not every rectangle is a square, since a rectangle's sides do not all have to match.
The parallelogram family is even bigger. Every parallelogram has two pairs of parallel, equal-length sides. A rectangle is a parallelogram that also has 4 right angles. A rhombus is a parallelogram that also has 4 equal sides. A square has both extras, so it is a rectangle and a rhombus at the same time.
To sort a shape, check which rules it passes. If it passes a family's rules, it belongs there, even when it also fits inside a smaller, more exact family.
A shape belongs to every family whose rules it meets, from the biggest group down to the most exact match.
The new play area is on paper now. Last time you sorted shapes the two-part way: sides first, then angles. Mia has drawn the sandpit 4 m along every side, with a square corner at each corner.
Start with the biggest family. Does the sandpit pass the parallelogram test?
Jobs that lean on this skill. Follow one to see everything it is built on.
18 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.