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📐 Mathematics  ·  Linear Programming  ·  JEE

For the diet problem with constraints 2x + y >= 8, x + 2y >= 11, x >= 0, y >= 0 and cost Z = 50x + 70y, the relevant corner points are (0,8), (5/3, 14/3), and (11,0). What is the minimum cost?

Answer: 410 at (5/3, 14/3).

  • A 410 at (5/3, 14/3)
  • B 560 at (0,8)
  • C 550 at (11,0)
  • D All three give the same minimum

Correct answer: A. 410 at (5/3, 14/3)

Explanation: Z(0,8) = 50(0)+70(8) = 560. Z(11,0) = 50(11)+70(0) = 550. Z(5/3,14/3) = 50(5/3)+70(14/3) = 250/3+980/3 = 1230/3 = 410. The minimum cost is 410 at (5/3, 14/3).

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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