A) 15
B) \[15\sqrt{3}\]
C) \[10\sqrt{3}\]
D) \[10\]
Correct Answer: D
Solution :
Let AB be the tree of height h feet and breadth of river be\[x\]feet. From \[\Delta ABC,\] \[\tan 60{}^\circ =\frac{h}{x}\] \[\Rightarrow \] \[h=\sqrt{3}x\] ?..(i) and in \[\Delta ABD,\] \[\tan 30{}^\circ =\frac{h}{x+20}\] \[\Rightarrow \] \[\frac{1}{\sqrt{3}}=\frac{h}{x+20}\] \[\Rightarrow \] \[x+20=\sqrt{3}h\] \[\Rightarrow \] \[x+20=3x\] [from Eq. (i)] \[\therefore \] \[2x=20\] \[\Rightarrow \] \[x=10\] \[\therefore \]Breadth of river is 10 ft.You need to login to perform this action.
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