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20 multiple-choice questions and 24 flashcards on Area of Polygons (Composing and Decomposing), about 13% of the 6th Math: Geometry bank. Every one carries a written rationale.
Area of Polygons (Composing and Decomposing) is one of 4 chapters in CoStudy's 6th Math: Geometry bank, and it holds 20 of the bank's 150 multiple-choice questions — roughly 13% 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.
5 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.
A parallelogram has area 60 and base 12. Its height is:
Answer: A — 5
A) 60 = 12h, h = 5. B) Doubled. C) Divided wrong way. D) Added.
Area of a triangle with base 12 and height 8:
Answer: A — 48
A) A = ½bh = ½(12)(8) = 48. B) Forgot the ½. C) Added base + height. D) Used a wrong factor.
An obtuse triangle has base 12 with height (perpendicular distance from base extension to opposite vertex) 5. Its area is:
Answer: A — 30
A) ½(12)(5) = 30 (use perpendicular height even when outside the triangle). B) Sum. C) Forgot ½. D) Wrong product.
A triangle has base 14 in and height 9 in. Its area is:
Answer: A — 63 in²
A) A = ½bh = ½(14)(9) = 63. B) Added base + height. C) Forgot the ½ (rectangle). D) Used the perimeter idea (2(b+h)).
A triangle has base 5 cm and height 8 cm. The area in cm² is:
Answer: D — 20
D) ½(5)(8) = 20. A) Sum of sides. B) Perimeter of related rectangle. C) Forgot ½.
3 cards from the 24 in this chapter.
Area of a rectangle 8 by 5?
40 square units.
Find the area of a trapezoid with bases 5 and 7, height 4.
24 sq units. ((5+7)/2 × 4 = 6 × 4 = 24.)
What is the formula for the area of a triangle?
A = (1/2) × base × height. Or A = bh/2.
These are a sample. The full Area of Polygons (Composing and Decomposing) chapter runs 44 items with per-chapter progress tracking, on the web and in the iOS app.
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