Grade 9: Space

Warm up with a few quick space warm-ups on the board while the class settles, so every child starts thinking about the skill.

An algorithm is a precise, step-by-step procedure for solving a problem. In geometry, algorithms describe how to sort shapes by their properties, test whether two shapes are congruent, carry out a construction, or solve a spatial problem, always in the same reliable order. Model the method clearly, thinking aloud:

• Start with a familiar sorting task (e.g. sort shapes by number of sides) and write down the exact steps used, in order.
• Introduce a congruence-testing algorithm: measure all three sides of each triangle, then compare the two sets for an exact match (SSS).
• Use a flowchart to show decision points explicitly, e.g. 'do all three sides match? yes -> congruent, no -> not congruent'.
• Emphasise that a good algorithm gives the SAME correct answer every time it is followed, with no guesswork.
• Practise writing an algorithm for a new problem (e.g. classifying a quadrilateral) before checking it against a worked example.

Do the first few questions of the practice worksheet together, one child explaining each step. Check for understanding before releasing the class to work alone.

Students complete the practice worksheet independently while you circulate and support.

Circulate and look for these, they are the usual sticking points:

• Skipping or reordering steps because a shortcut 'looks' right for one example.
• Writing an algorithm with a missing decision point, so it cannot handle every case.
• Assuming an algorithm that works for one type of shape automatically works for all shapes.
• Describing what the algorithm's GOAL is, rather than the actual step-by-step procedure to get there.

Pull the class back together. Ask one child to explain space in their own words, pose a single check question everyone answers on a mini whiteboard, and name what you will build on next lesson.

Use the independent worksheet as the evidence. A child who can complete it accurately and explain one answer has met the objective; anyone who cannot needs the easier level and a short reteach next session.