Home Models & Strategies · Grades 3–4 2D Figures: Six Tests That Name a Shape Six tests you run on a figure, from counting its sides to the family tree that lets one shape hold four names at once. Count the straight sides. That number is what names the figure.circleno straight sidestriangle3 sidesquadrilateral4 sidespentagon5 sideshexagon6 sidesa circle has no straight sides, so it is not a polygonthe count names it, however it is turnedany four-sided polygon is a quadrilateral: say that, not “diamond” or “box” Count the straight sides Read this one Do two sides run the same way forever without ever meeting?PARALLEL SIDESparallelogram2 pairstrapezoid1 pairNO PARALLEL SIDESquadrilateral0 pairstrianglenever anythe amber sides are the parallel onesthree sides cannot make a pairparallel is about a PAIR of sides, so one side alone is never parallel Parallel sides Read this one Does any corner make a square corner? That is a right angle.HAS RIGHT ANGLESrectangle4 of themright trapezoid2 of themHAS NONErhombus0triangle0two sides meeting at a right angle are perpendicularequal sides do not make square cornersperpendicular and right angle are the same test, said two ways Right angles Read this one Measure every angle against a square corner. The biggest one decides.THE MEASURING STICKright triangleone square cornerexactly one angle is a right angleCOMPARED TO ITacuteall three smallerobtuseone is biggeronly the biggest angle decides the namea triangle has at most ONE angle that is right or bigger; the other two must fit Angles against a right angle Read this one Fold it. Does one half land exactly on top of the other?square4 fold linesrectangle2 fold linestriangle1 fold lineparallelogramnone at alla fold line may be slanted, not only up and acrossnot every triangle has onea parallelogram never doesturning a shape onto itself is not folding it; only a fold counts here Lines of symmetry Read this one A square is a rectangle AND a parallelogram AND a quadrilateral, all at once.quadrilateralparallelogramrectanglesquareeach ring inside adds one more rulesquare → rectangle ✓rectangle → parallelogram ✓rectangle → square ✗the arrow runs from the special shape to the general onea rhombus is a parallelogram too“Is it a rectangle?” and “Is it a square?” are two different questions One shape, many names Read this one