Similar-triangles under the same Sun — pole and man comparison: A vertical pole 6 m high casts an 8 m shadow. At the same time and place, a man nearby casts a 2.4 m shadow. What is the height of the man (in meters)?
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A1.4 m
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B1.6 m
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C1.8 m
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D2.0 m.
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E1.5 m
Answer
Correct Answer: 1.8 m
Explanation
Introduction / Context:When two vertical objects cast shadows at the same time, similar triangles apply: height/shadow is constant. We can scale the man’s shadow by the known ratio from the pole to find the man’s height.
Given Data / Assumptions:
- Pole height = 6 m; its shadow = 8 m
- Man’s shadow = 2.4 m; man’s height = ?
- Same Sun (same solar elevation), level ground.
Concept / Approach:Use height/shadow = constant for both objects (similar right triangles). Thus hman / 2.4 = 6 / 8.
Step-by-Step Solution:hman = 2.4 × (6/8) = 2.4 × 0.75 = 1.8 m
Verification / Alternative check:Both give the same tangent ratio: 6/8 = 1.8/2.4 = 0.75, confirming the similarity scaling is correct.
Why Other Options Are Wrong:Values 1.4, 1.6, 2.0, or 1.5 m do not preserve the same height-to-shadow ratio with a 2.4 m shadow.
Common Pitfalls:Inverting the ratio (8/6 instead of 6/8); mixing units (they are already in meters).
Final Answer:1.8 m