A man is walking away from a lamppost with a light source h = 6 m above the ground. The man is m = 1.5 m tall. How long is the man's shadow when he is d = 11 m from the lamppost? (Hint: Use similar triangles.)

1 answer

  1. Let the man's shadow length be x.

    Draw the figure showing how the shadow is cast.

    Similar triangles should tell you that
    6/(11 + x) = 1.5/x

    Solve for x

    6x = 33/2 + 3x/2
    9x/2 = 33/2

    x = 33/9 = 11/3 = 3.667 m

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