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6th Class Mathematics Mensuration Question Bank Mensuration Basics

  • question_answer
    The length of a rectangular field is increased by 60% and its breadth is decreased by 40% to form a new rectangular field. Find the percentage change in the area of the field.

    A)  \[20%\]measure         

    B)  \[4%\]decrease    

    C)  \[20%\]decrease         

    D)  \[4%\]increase

    Correct Answer: B

    Solution :

    \[\left. \begin{align}   & 1\to 1\times \left( 1+\frac{60}{100} \right)=1.61 \\  & b\to b\times \left( 1-\frac{40}{100} \right)=0.6\,b \\ \end{align} \right\}\]old area \[l\times b,\]new area\[=1.61\times 0.6b=(0.96)lb\] \[\therefore \]Percentage decrease \[=lb-0.96\text{ }Ib=0.04=4%\]


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