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It is found that on walking $20$ m towards a chimney in a horizontal line through its base, the elevation of its top changes from $30^\circ$ to $60^\circ$. The height of the chimney is :
- (a)$20\sqrt{3}$ m
- (b)$10\sqrt{3}$ m
- (c)$\frac{20\sqrt{2}}{3}$ m
- (d)$\frac{20}{\sqrt{3}}$ m
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Ans. (b) $10\sqrt{3}$ m