Direct tan from distance and elevation — tower height A tower stands on level ground. From a point 100 m from its base, the angle of elevation of the top is 30°. What is the tower’s height?
Aptitude
Height and Distance
Difficulty: Easy
Choose an option
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A100 m
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B100 √3
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C100/ √3
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DNone of these
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E—
Answer
Correct Answer: 100/ √3
Explanation
Introduction / Context:This is a basic height–distance application of right-triangle trigonometry using the tangent function.
Given Data / Assumptions:
- Horizontal distance d = 100 m.
- Angle of elevation θ = 30°.
- Ground level and vertical tower.
Concept / Approach:In a right triangle, tan θ = opposite/adjacent = height/distance. Therefore, height h = d · tan θ.
Step-by-Step Solution:
tan 30° = 1/√3h = 100 * (1/√3) = 100/√3 mVerification / Alternative check:As θ is small (30°), height should be less than distance, which it is (≈ 57.7 m).
Why Other Options Are Wrong:100√3 is too large; 100 m would imply tan 30° = 1; “None” is incorrect because 100/√3 is present.
Common Pitfalls:Using sin instead of tan; mixing up opposite and adjacent legs.
Final Answer:100/ √3