Math Puzzles

Can you help the spider?


*Please note that the original solution provided had an error. Thanks to our teacher partner Shilpa Kulkarni, the correct solution has been found:

If the spider walks upward across the right wall (even with an infinitesimal movement), reaches the right edge and then comes down towards the bee, the shortest path will be marginally more than 33.

Can you solve this question?

A spider is on the floor in one corner of the room. A fly settles in the diagonally opposite corner. The spider needs to take the shortest route to the fly, without walking on any part of the floor! How far does the spider have to walk?

Download the PDF for the solution of the Puzzle.

📥  Can you help the spider?


question based on spider

This was the original explanation (as provided in the book):
You will find this puzzle difficult to solve if you continue to visualize it in 3-D. Rather, you should make an attempt to reduce this to 2-D. To do this, unfold the walls and the ceiling of the room and lay them out flat out (imagine that you are on the top of the ceiling watching from above and pulling all the walls upward):


The images show the spider and the fly at two places because they are placed at corners (shared by two walls).
From the figure, it becomes clear that the spider will need to take the A-B in order to reach the fly (the shortest path possible between two points is the straight line connecting the two points).

AB is calculated using the Pythagoras theorem:

AB = (262 + 232)1/2 = 34.71

Note that other possible paths are CB and AD. Can you check if these paths are longer than AB?

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