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📐 Mathematics  ·  Linear Programming  ·  JEE

A factory produces two products A and B. Each unit of A needs 3 machine-hours and 1 labour-hour; each unit of B needs 1 machine-hour and 2 labour-hours. Only 12 machine-hours and 10 labour-hours are available daily. Which constraint pair models this?

Answer: 3x + y = 0.

  • A 3x + 2y <= 12 and x + y <= 10, x,y >= 0
  • B 3x + y >= 12 and x + 2y >= 10, x,y >= 0
  • C x + 3y <= 12 and 2x + y <= 10, x,y >= 0
  • D 3x + y <= 12 and x + 2y <= 10, x,y >= 0

Correct answer: D. 3x + y <= 12 and x + 2y <= 10, x,y >= 0

Explanation: Machine-hours: 3 per unit of A plus 1 per unit of B, limited to 12, giving 3x + y <= 12. Labour-hours: 1 per A plus 2 per B, limited to 10, giving x + 2y <= 10.

Feasible Region and Corner PointsxyOABCfeasible regionZ = ax+by is evaluated ONLY at corners O, A, B, C - the optimum is always at one of these

The feasible region (shaded) is bounded by the constraint lines; the fundamental theorem of LPP guarantees the optimal value of the objective function occurs at one of the corner points (O, A, B, C), so only these need to be checked, not the entire region.

Concept context

Optimizing a linear objective function subject to linear constraints using the graphical corner point method.

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