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10 multiple-choice questions and 7 flashcards on Similarity, about 7% of the High School Geometry bank. Every one carries a written rationale.
Similarity is one of 13 chapters in CoStudy's High School Geometry bank, and it holds 10 of the bank's 150 multiple-choice questions — roughly 7% of the total. That proportion is not arbitrary: chapters follow the certifying body's published exam outline, and the number of questions in each is set by that domain's published weight, so the share of your practice time this chapter takes matches the share of the real exam it accounts for.
Studying by chapter is worth doing once you have a diagnostic score. A single overall percentage tells you whether you are close; it does not tell you which domain is dragging. Working a weak chapter in isolation, and re-testing it in isolation, is the fastest way to move a score that has stalled — and it is why the mock exams in CoStudy report by domain rather than as one number.
3 questions drawn from this chapter, with the full rationale shown — the controlling principle behind the right answer, and why each wrong option tempts and fails.
Two triangles have angles 50°, 70°, 60° and 50°, 70°, 60°. By which theorem are they similar?
Answer: B — AA Similarity
A) SSS Similarity requires proportional sides — none given. B) AA Similarity: two pairs of equal angles ⇒ similar (third pair forced by angle sum). C) SAS Similarity requires a proportional side pair plus the included angle. D) HL is a congruence theorem for right triangles, not a similarity criterion.
Distance between (1, 2) and (4, 6):
Answer: E — 5 (d = √((4-1)² + (6-2)²) = √(9+16) = √25 = 5)
Distance formula: d = √((x₂-x₁)² + (y₂-y₁)²). Differences 3 and 4. Sum of squares 25. √25 = 5. (3, 4, 5) Pythagorean triple in disguise.
In △ABC, DE is parallel to BC with D on AB and E on AC. If AD = 3, DB = 6, AE = 4, then EC equals:
Answer: D — 8
A) Took AD/AE instead of using the side-splitter ratio. B) Forgot the correct correspondence. C) Computed DB · AE / AD incorrectly. D) Side-Splitter Theorem: AD/DB = AE/EC, so 3/6 = 4/EC, giving EC = 8.
3 cards from the 7 in this chapter.
In similar triangles, what's the ratio relationship for sides?
All corresponding sides are in the same ratio (the scale factor).
What does 'similar' (~) mean?
Same shape but not necessarily same size. Corresponding angles equal; corresponding sides proportional.
What is the AA Similarity Postulate?
If two angles of one triangle equal two angles of another, the triangles are similar.
These are a sample. The full Similarity chapter runs 17 items with per-chapter progress tracking, on the web and in the iOS app.
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