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)?

Difficulty: Easy

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

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