Two poles stand vertically on level ground. One is 10 feet tall, the other 15 feet tall. If a line is drawn from the top of each pole to the bottom of the other, the two lines intersect at a point 6 feet above the ground. What’s the distance between the poles?You can take a wild guess (and be correct), or view the answer at Futility Closet.
Addendum: If you're like me and need a bit of help in understanding the answer, see the comment by the fourth Anonymous (8:28 PM), which refers to this annotated version of the same diagram: