JEE Advanced Mathematics question
A vertical lamp-post, 6 m high, stands at a distance of 2 m from a wall, 4 m high. A 1.5-m-tall man starts to walk away from the wall on the other side of the wall, in line with the lamp-post. The maximum distance to which the man can walk remaining in the shadow is
Answer: (A)
Solution
*(Figure: lamp-post PQ = 6 m at Q; wall AB = 4 m at B with QB = 2 m; man CD = 1.5 m at D beyond the wall; the light ray from P through the wall top A meets the ground at R, passing through the man's head C at the limiting position.)*
The ray from P through A meets the ground at R. By similar triangles (PQR ~ ABR):
{
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