Here's a brain test for you.
Take a look at the picture below [the picture is not to scale].
What you are looking at is a picture of 2 black poles sitting in the green ground. The black poles stick out of the ground 4 meters.
There is a brown rope strung between the poles, and it is 2 meters long.
The brown rope hangs down 1 meter.
Question: What is the distance between the poles?
Answers can be left in the comments. First one to get it right gets the grand reward of the admiration of their peers. Sort of! Anyway, here is the picture: