Mathematics Geometry Procedural 9–10 yrs

Understanding angles (age 9+)

理解角度（9岁以上）

Description

Use the properties of rectangles to deduce related facts and find missing lengths and angles

Mastery Evidence

✓ Given one side of a rectangle is 8 cm and the perimeter is 28 cm, find the other side
✓ Explain that all angles in a rectangle are 90°
✓ Find a missing side of a rectangle given its area and one side length

Assessment Prompt

If your child knows one side of a rectangular garden is 7 m, can they tell you the length of the opposite side and all four corner angles — without measuring?