Q1. [1] § 9.1 Heights and Distances § 9.2 Summary
An observer 1.8 m tall stands away from a chimney at a distance of 38.2 m along the ground. The angle of elevation of top of chimney from the eyes of observer is 45°. The height of chimney above the ground is
- A 38.2 m
- B 36.4 m
- C 40 m
- D $(38.2)\sqrt{2}$ m
Previously asked in CBSE board exam
2025 30/5/1 Q13
Generated by claude-sonnet-4-6 · 2026-06-15 10:37 · grounding rag
Model Answer
Option C: 40 m
Using tan 45° = 1, the horizontal distance from observer's eyes to chimney = 38.2 m. So the chimney height above eye level = 38.2 m. Total height = 38.2 + 1.8 = 40 m.
Explanation
This follows the same method as Example 3 in the textbook. The observer's eye level is 1.8 m above the ground. Since tan 45° = 1, the vertical rise from eye level equals the horizontal distance (38.2 m). Add the observer's height (1.8 m) to get the total chimney height: 38.2 + 1.8 = 40 m. Always remember to add the observer's height to the calculated vertical distance to get the height above ground.
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