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12 multiple-choice questions and 10 flashcards on Greatest Common Factor and Least Common Multiple, about 8% of the 6th Math: The Number System bank. Every one carries a written rationale.
Greatest Common Factor and Least Common Multiple is one of 6 chapters in CoStudy's 6th Math: The Number System bank, and it holds 12 of the bank's 150 multiple-choice questions — roughly 8% 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.
Which set lists the factors of 20?
Answer: A — 1, 2, 4, 5, 10, 20
A) Complete factor list of 20. B) Missing 1 and 20; includes 6 (not a factor). C) Missing 10. D) Missing 2 and 4.
LCM of 9 and 15.
Answer: D — 45
B) Multiples of 9: 9,18,27,36,45; of 15: 15,30,45. LCM = 45. A) GCF. C) Product. B) Sum.
What is the GCF of 12 and 18?
Answer: C — 6
Factors of 12: 1,2,3,4,6,12. Factors of 18: 1,2,3,6,9,18. GCF = 6. (A), (B), (D) miscalculate.
4 cards from the 10 in this chapter.
What is the LCM of 9 and 12?
36.
Which is greater: −10 or 1?
1.
Worked example: Find the GCF of 24 and 36.
Step 1: Prime-factor each number. 24 = 2 × 2 × 2 × 3 = 2³ · 3 36 = 2 × 2 × 3 × 3 = 2² · 3² Step 2: Take the LOWEST power of each shared prime: Shared 2: min(3, 2) = 2 → 2² = 4 Shared 3: min(1, 2) = 1 → 3¹ = 3 Step 3: Multiply: 4 × 3 = 12. Answer: GCF = 12.
Plot (−3, 4) — which quadrant?
Quadrant II.
These are a sample. The full Greatest Common Factor and Least Common Multiple chapter runs 22 items with per-chapter progress tracking, on the web and in the iOS app.
Open 6th Math: The Number System in CoStudy →