Difficulty: Medium
Correct Answer: 25 √3 m
Explanation:
Introduction / Context:Shadow length s = H cot θ for a vertical object. Two altitudes give two shadows; their difference is known, allowing H to be solved exactly.
Given Data / Assumptions:
Concept / Approach:s30 = H cot 30° = H √3; s60 = H cot 60° = H / √3. Their difference equals 50 → solve for H.
Step-by-Step Solution:
s30 − s60 = H(√3 − 1/√3) = 50.√3 − 1/√3 = (3 − 1)/√3 = 2/√3.Thus H * (2/√3) = 50 → H = 25 √3 m.Verification / Alternative check:Compute shadows with H = 25√3: s30 = 75; s60 = 25 → difference 50 ✔️.
Why Other Options Are Wrong:20√3 and 25/√3 give wrong differences; duplicate 20√3 is a distractor.
Common Pitfalls:Using tan instead of cot for shadow; subtracting in reverse (negative); arithmetic slip when simplifying 2/√3.
Final Answer:25 √3 m
Discussion & Comments