8th grade · Geometry
Use informal arguments to establish facts about the angle sum and exterior angle of triangles, about the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles. *For example, arrange three copies of the same triangle so that the sum of the three angles appears to form a line, and give an argument in terms of transversals why this is so*.
2 interactive, auto-graded activities for 8th grade students practising 8.G.A.5. Mini Labs put the standard to work in a real scenario; Skill Practice builds fluency on the standard alone. Every one is randomized per student, so each learner gets their own numbers.
Students join the Riverton road crew to find the missing corners of ten triangular traffic islands. They use the triangle angle sum (180°) and the exterior angle theorem, while a running total catches slips like 185° before they move on. Correct angles label the island drawing. Auto-graded, randomized, Grade 8, 8.G.A.5.
Students join the Riverton road crew and use angle relationships to find all eight corners where a diagonal avenue crosses two parallel streets. They name the rule for each angle (corresponding, alternate interior, same-side interior, vertical, linear pair), enter the measure, and watch the map fill in. Two crossings add solving for x. Auto-graded, randomized, 8.G.A.5.
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