lesson
Classify by properties
1 · Learn
An equilateral triangle has three equal sides. An isosceles triangle has at least two equal sides. A scalene triangle has no equal sides. Classifications can overlap under this inclusive definition.
A rectangle has four right angles; a square also has four equal sides, so it is a special rectangle. A rhombus has four equal sides but need not have four right angles.
2 · Worked example
A tilted square is still a square. Rotation changes its position, not its side lengths or angles.
3 · Your turn
A quadrilateral has four right angles and sides 6 cm, 3 cm, 6 cm, 3 cm. Is it a rectangle? Is it a square?
Check your answer
It is a rectangle but not a square, because not all four sides are equal.
4 · Apply your learning
Sort measured shape drawings using stated properties. Explain overlapping groups and the definitions your class uses.
Adult guidance and safety
Use practical or drawn representations and explain the method. Check units and labels. A correct answer to one example is not evidence of secure fluency; revisit with varied numbers and feedback.
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