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7th Class Mental Ability Algebraic Expressions Question Bank Algebra

  • question_answer
    Find the dimension of rectangle when its length is 20 m more than its width. If its width is reduced by 20 m and length is increased by 100 m then the perimetre will be twice the perimetre of original one.

    A) 30 m, 50 m

    B)               40 m, 60 m

    C) 20 m, 40 m

    D)               10 m, 30 m

    E) None of these

    Correct Answer: C

    Solution :

    Explanation Let the breadth of rectangle be x. Then length will be \[\operatorname{x} + 20\] According to question \[2\left( x + 100 + x - 20 \right) = 2\left[ 2\left( x + x + 20 \right) \right]\] \[\Rightarrow \,\,\,2 \left( 2x + 80 \right) = 4\left( 2x + 20 \right)\] \[4x + 160 = 8x + 80\] \[4x = 80\] \[\Rightarrow \,\,\,x=20\] \[\operatorname{breadth} = 20m\] \[\operatorname{length} = 20 + 20 = 40 m.\]


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