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Ashish Solanki

· started a discussion

· 1 Months ago

Q - 5 QUANT SECTIONAL TEST - 4 SSC CGL TIER 1 - NO FIGURE (Question: 111090.0 )

IN THE EXPLANATION THERE IS NO FIGURE IS GIVEN OVER WHICH THE SOLUTION IS EXPLAINED. PLEASE PROVIDE FIGURE FOR THE QUESTION.

Question:

A person standing on the bank of a river observes that the angle of elevation of the top of a tree standing on the opposite bank is 60o. When he moves 20 meters away from the bank, he finds the angle of elevation to be 30o. The width of the river are.

      
Options:
A) 10 m
B) \(10\sqrt[]{3}\) m
C) 20 m
D) \(20\sqrt[]{3}\) m
Solution:
Ans: (a)


In ΔCAB,
Tan 60o = h / x
⇒ √3 = h / x.
⇒  h = √3x -----(i)
In ΔDAB,
Tan 30o = h / (20 + x)
⇒ 1 / √3 = h / (20 + x)
⇒  (20 + x) = √3h -----(ii)
Substituting h = √3x  in equation (ii)
⇒  (20 + x) = √3x√3x
⇒  (20 + x) = 3x
2x = 20
x = 10.
There fore ,width of the river = 10 meters

Knowledge Expert

· commented

· 1 Months ago

Dear student
We have updated the question and solution both,
please solve it again.

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