Let us guess, this is how you cut a birthday cake isn't it? Obviously. It's classic.
IT'S ALSO WRONG.
"The reason why this is a really bad way to cut a cake is [the now exposed sides] are just going to get dry," Alex Bellos, author of The Grapes of Math: How Life Reflects Numbers and Numbers Reflect Life, explains in this video for Numberphile.
The next day, when you cut a second wedge from the cake, one side of that wedge will be dry. He says, "You're not maximizing the amount of gastronomic pleasure that you could make from this cake. There is a better way."
This is that better way: First, you cut horizontally across the cake.
"It's breaking all the rules!" Alex says, calling the piece, "The prime steak of that cake"
Cut across the cake horizontally once again and you have your piece.
Now, you can push the two halves of the cake together with nothing exposed!
This method comes from a 1906 article in Nature magazine, called "Cutting a Round Cake on Scientific Principles." It called the typical method "faulty" and in more scientific verbiage says:
"The results to be aimed at are so to cut the cake that the remaining portions shall fit together. Consequently the chords (or the arcs) of the circumferences of these portions must be equal...[These cuts] represent those made with the intention of letting the cake last for three days, each successive operation having removed about one-third of the area of the original disc."
The article suggests holding the remaining halves together with a rubber band. The next day, when you want to cut the cake again, you just cut it horizontally in the other direction, then push the four wedges together, as such:
Mind blown! Watch the entire process in the video below: