JEE Main & Advanced Mathematics Conic Sections Question Bank Self Evaluation Test - Conic Sections

  • question_answer
    If two circles A, B of equal radii pass through the centres of each other, then what is the ratio of the length of the smaller are to the circumference of the circle A cut off by the circle B?

    A) \[\frac{1}{2}\]

    B) \[\frac{1}{4}\]

    C) \[\frac{1}{3}\]

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

    Correct Answer: C

    Solution :

    [c] When two circles A and B of equal radii pass through the centers of each other. The angle made by arc of B at the centre of B is\[90{}^\circ \]. So, length of small are of B= \[\frac{2\pi 90{}^\circ }{360{}^\circ }=\frac{\pi r}{2}\] Hence, circumference of A cut off by the circle B \[=2\pi r-\frac{\pi r}{2}=\frac{3\pi r}{2}\] \[\therefore \] Required ratio \[=\frac{\pi r/2}{3\pi r/2}=\frac{1}{3}\]


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