A) 20 m
B) 10 m
C) 5 m
D) 1 m
Correct Answer: B
Solution :
Let \[h\] m be the height of tree CD and \[x\,m\]be the width of river. In \[\Delta BCD\] \[\tan {{60}^{o}}=\frac{CD}{BC}\] \[\Rightarrow \] \[\sqrt{3}=\frac{h}{x}\] \[\Rightarrow \] \[h=\sqrt{3}x\] ?(i) and in \[\Delta \Alpha CD\] \[\tan {{30}^{o}}=\frac{CD}{AC}\] \[\Rightarrow \] \[\frac{1}{\sqrt{3}}=\frac{h}{x+20}\] \[\Rightarrow \] \[x+20=h\sqrt{3}\] \[\Rightarrow \] \[3x=x+20\][using Eq.(i)] \[\Rightarrow \] \[x=10\] \[\therefore \]Width of river \[=10\,m\]You need to login to perform this action.
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