Real Mathematics – Geometry #8

Right way to cut a round cake

Almost everyone thinks of the same shape when someone mentions “a slice of round cake”:

However, this is not the correct way to cut a round cake. A letter was published in Nature magazine in December 20, 1906. It was written by a famous British scientist Francis Galton. Galton claimed that traditional way of cutting a round cake was faulty as after the cut exposed surfaces of the cake would start becoming dry almost instantly.

Francis Galton’s letter.

Therefore he claimed that he found a “scientific principle” to cut a round cake.

Scientific way of cutting a cake is shown below:


First Blood: Imagine two lines that are both parallel to the diameter and only a short distance away from it. As Galton suggested, one should cut the cake through these imaginary lines. Hence, exposed surfaces are same and they could be brought together. In order to keep the cake at a stable one piece position, you could use a rubber band.

Second Cut: You can do that like the first cut, but perpendicular to those cuts. In the end you would end up with four pieces of cake. They can be stuck together with a rubber band again.

This is the “scientific” way to keep your cake fresh.

In case you’d like to try Galton’s method without using a cake, all you need is a circle drawn on a paper:

One wonders…

Assume that you are on a Sunday brunch with your friends and pancakes arrived to the table. You realized that the waiter brought one extra pancake and everyone in the table wants that freebee.


You all agreed to play a game in order to decide who gets the pancake.

Game: Everyone has a pancake on their plate. Everyone will try to cut his/her pancake to most pieces with three straight cuts. (You are not allowed to move the pieces of the pancake.) Winner(s) will get the pancake.

M. Serkan Kalaycıoğlu

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