JEE Main & Advanced Sample Paper JEE Main Sample Paper-31

  • question_answer
    The figure show a \[\Delta AOB\] and the parabola\[y={{x}^{2}}\]. The ratio of the area of the \[\Delta AOB\] to the area of the region AOB of the parabola \[y={{x}^{2}}\], is equal to

    A) \[\frac{3}{4}\]     

    B) \[\frac{3}{5}\]

    C) \[\frac{5}{6}\]

    D)                                    \[\frac{2}{3}\]

    Correct Answer: A

    Solution :

    Area of curve \[OAB=\int\limits_{a}^{{{a}^{2}}}{xdy}=2\int\limits_{a}^{{{a}^{2}}}{\sqrt{y}}dy=\frac{4}{3}({{a}^{3}})\] Also, area of \[\Delta OAB=\frac{1}{2}(2a)({{a}^{2}})={{a}^{3}}\] \[\therefore \frac{\text{area}\,\,\text{of}\,\,\Delta \text{OAB}}{\text{area}\,\,\text{of}\,\,\text{curve}\,\,\text{OAB}}\text{=}\frac{{{\text{a}}^{\text{3}}}}{\frac{\text{4}}{\text{3}}{{\text{a}}^{\text{3}}}}\text{=}\frac{\text{3}}{\text{4}}\]


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