Question 41

The time required for a boy to travel along the external and internal boundaries of a circular path are in the ratio 20: 19. If the width of the path be 5 metres, the internal diameter is:

Solution

Let internal radius of the path be $$r$$ m and thus external radius = $$(r+5)$$ m

As, distance $$\propto$$ time

=> $$\frac{2\pi (r+5)}{2\pi r}=\frac{20}{19}$$

=> $$19r+95=20r$$

=> $$20r-19r=r=95$$

$$\therefore$$ Internal diameter = $$2\times95=190$$ m

=> Ans - (D)

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