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From a point $P$ on the ground, the angle of elevation of the top of a $10\mathrm{m}$ building is $30^{\circ}$. What is the distance of the building from $P$? 
A$\frac{10}{\sqrt{3}}\mathrm{m}$
B$10\sqrt{3}\mathrm{m}$
C$20\mathrm{m}$
D$20\sqrt{3}\mathrm{m}$
Answer & Solution
Correct answer: B. $10\sqrt{3}\mathrm{m}$
If the horizontal distance is $x$, then $\tan 30^{\circ}=\frac{10}{x}=\frac{1}{\sqrt{3}}$. Therefore $x=10\sqrt{3}\mathrm{m}$.
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