JEE Main & Advanced Mathematics Linear Programming Question Bank Self Evaluation Test - Linear Programming

  • question_answer
    Maximize \[Z=3x+5y,\] subject to \[x+4y\le 24,\]\[3x+y\le 21,\]\[x+y,\le 9,\]\[x\ge 0,y\ge 0,\] is

    A) \[20\,at\,(1,0)\]

    B) \[30\,\,at\,\,(0,6)\]

    C) \[37\,at\,(4,5)\]

    D) \[33\,\,at\,\,(6,3)\]

    Correct Answer: C

    Solution :

    [c] We have, maximize \[Z=3x+5y\]subject to constraints:\[x+4y\le 24,3x+y\le 21,x+y\le 9,x\ge 0,y\ge 0\]
    Let \[{{\ell }_{1}}:x+4y=24\]
    \[{{\ell }_{2}}:3x+y=21\]
    \[{{\ell }_{3}}:x+y=9\]
    \[{{\ell }_{4}}:x=0\] and \[{{\ell }_{5}}:y=0\]
    On solving these equations we will get points as
    O (0, 0), A (7, 0), B (6, 3), C (4, 5), D (0, 6)
    Now maximize \[Z=3x+5y\]
    \[ZatO(0,0)=3(0)+5(0)=0\]
    \[ZatA(7,0)=3(7)+5(0)=21\]
    \[ZatB(6,3)=3(6)+5(3)=33\]
    \[ZatC(4,5)=3(4)+5(5)=37\]
    \[ZatD(0,6)=3(0)+5(6)=30\]
    Thus, Z is maximized at C (4, 5) and its maximum value is 37.


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