6th Class Mathematics Mensuration Question Bank Menstruation

  • question_answer
    If the length of a rectangle is increased by 50% and its breadth is decreased by 25%, what is the change percent in its area?

    A)  12.5% increase

    B)                10% increase

    C)  25% increase             

    D)  20% increase

    Correct Answer: A

    Solution :

         Let the initial length and the breadth of the rectangle be x and y respectively. \[\therefore \]    Initial area \[=xy\] Now, new length \[=x+x\times \frac{50}{100}\,=\frac{3x}{2}\] And new breadth \[=y-y\times \frac{25}{100}=\frac{3y}{4}\] \[\therefore \] New area \[=\frac{3x}{2}\,\times \frac{3y}{4}=\frac{9xy}{8}\] Clearly, new area is more than the initial area. \[\therefore \]    Increarnent in percent in area \[=\frac{\frac{9xy}{8}-xy}{xy}\,\times 100%=12.5%\]


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