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A person walks one lap along a circle at a speed vv. Thereafter, he runs one lap along the boundary of the largest square that can be inscribed in the circle at a speed 3v3v. The ratio of the time he walks to the time he runs is

Solution

Correct Option: 4

Let the radius of the circle be rr.

Circumference (walking distance) =2πr= 2\pi r.


The largest square inscribed in the circle has its diagonal equal to the diameter 2r2r.

Side of square =2r2=r2= \dfrac{2r}{\sqrt{2}} = r\sqrt{2}

Perimeter (running distance) =4r2= 4r\sqrt{2}


Time walking ==

2πrv\dfrac{2\pi r}{v}

Time running ==

4r23v\dfrac{4r\sqrt{2}}{3v}


Ratio of times:

2πr/v4r2/(3v)=2πrv3v4r2=6π42=3π22\dfrac{2\pi r / v}{4r\sqrt{2} / (3v)} = \dfrac{2\pi r}{v} \cdot \dfrac{3v}{4r\sqrt{2}} = \dfrac{6\pi}{4\sqrt{2}} = \dfrac{3\pi}{2\sqrt{2}}

Answer =3π22= \dfrac{3\pi}{2\sqrt{2}}

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