When someone at BOSS says there is a bug in the system, we normally start looking for a problem with the software. This time the bug is mechanical.
Deep in one of our data halls we have a small magnetic inspection robot, affectionately known as S.P.I.D.E.R. It can crawl across the walls, floor and ceiling, but it cannot jump or leave the surface.
One of the sensors at the far end of the hall has failed, and S.P.I.D.E.R has been sent to investigate.
It is programmed to minimise its travel time, but is unsure which route to take. It has messaged us to tell it the shortest route!
The puzzle
The data hall is a rectangular box:
- 20 metres long
- 6 metres wide
- 8 metres high
S.P.I.D.E.R. starts in the middle of one end wall, exactly 1 metre below the ceiling.
The faulty sensor is in the middle of the opposite end wall, exactly 1 metre above the floor.
Spider may crawl anywhere on the walls, floor or ceiling, but it must remain in contact with the surface at all times.
What is the shortest distance Spider needs to travel to reach the sensor?
And, perhaps more importantly:
How can you be certain that your route really is the shortest one?
Need a hint?
If you need a hint then click here to reveal it,, but we would really suggest trying the puzzle on your own first!
Hint 1
Imagine that the data hall is made from cardboard.
If you cut along some of its edges and unfold the surfaces Spider crosses until they lie flat, what happens to Spider’s shortest path?
Hint 2
The most obvious route is not the best one.
Try unfolding an end wall, one of the side walls, the floor and the opposite end wall.
Look for a right-angled triangle.
