9th Class Mathematics Polynomials Question Bank Polynomials

  • question_answer
    Length, breadth and height of a cuboidal tank are \[(x-3y)m,\,(x+3y)m\]and\[({{x}^{2}}+9{{y}^{2}})m\]  respectively. Find the volume of the tank.

    A) \[({{x}^{3}}+3xy+27{{y}^{3}}){{m}^{3}}\]

    B) \[({{x}^{4}}+2{{x}^{2}}{{y}^{2}}+81{{y}^{4}}){{m}^{3}}\]

    C) \[({{x}^{2}}-81{{y}^{4}}){{m}^{3}}\] 

    D) \[({{x}^{4}}+81{{y}^{4}}){{m}^{3}}\]

    Correct Answer: C

    Solution :

    Volume of cuboidal tank \[\text{=}\,\text{Length }\!\!\times\!\!\text{ breadth }\!\!\times\!\!\text{ height}\] \[(x-3y)(x+3y)({{x}^{2}}+9{{y}^{2}})\] \[=({{x}^{2}}-9{{y}^{2}})({{x}^{2}}+9{{y}^{2}})=({{x}^{4}}-81{{y}^{4}}){{m}^{3}}\]


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