Difficulty: Easy
Correct Answer: 6
Explanation:
Introduction / Context:
With equal efficiencies, work is proportional to (number of men) × (number of days). Equating two such products yields a quadratic that simplifies to a linear equation once expanded and common terms cancel.
Given Data / Assumptions:
Concept / Approach:
Expand both sides, cancel matching x^2 terms, and solve the resulting linear equation for x. Check that the resulting days are positive.
Step-by-Step Solution:
Left: (x + 2)(x − 3) = x^2 − x − 6Right: x(x − 2) = x^2 − 2xEquate: x^2 − x − 6 = x^2 − 2x ⇒ −x − 6 = −2x ⇒ x = 6
Verification / Alternative check:
Plug back: (6 + 2)(6 − 3) = 8*3 = 24 and 6*(6 − 2) = 6*4 = 24. Equality holds and days are positive.
Why Other Options Are Wrong:
4, 8, and 9 do not satisfy the equation; they create unequal work totals.
Common Pitfalls:
Arithmetic errors on expansion; ignoring feasibility (days must be positive).
Final Answer:
6
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