Two vertical poles of heights, 20m and 80m stand apart on a horizontal plane.

Question

Two vertical poles of heights, 20m and 80m stand apart on a horizontal plane. The height (in meters) of the point of intersection of the lines joining the top of each pole to the foot of the other, from this horizontal plane is:

Accepted Answer

This is a standard result: the intersection height $=\dfrac{h_1h_2}{h_1+h_2}$.

$$\frac{20\times80}{20+80} = \frac{1600}{100}=16\text{ m}$$

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