“When will we ever use this math in real life...” Life is full of ways to use math- in fact a major profit source for many businesses is figuring you can’t, or won’t do the math. They offer play math games intentionally to present the offer that is most advantageous to them- as most advantageous to you, and may obfuscate the math behind social engineering tricks designed to build additional value in to things where none exists, or make cross comparison of “apples to apples” impossible or skewed. Math is key to being a savvy consumer.
It’s not 24 inches of pizza vs 18. 24 inched is the diameter of the pizza. Imagine a line drawn through the center of the widest pout of the pizza. That line would be 18 it 13 inches in our example. It doesn’t account for the pizza on either side of the line. Just the line. Because a circle has fixed dimensions, as the diameter increases, the area (total amount) of the circle increases greatly in every direction. We aren’t concerned with just the diameter of the pizza, because we aren’t just going to eat the center most line of the pizza. If you make a circle of string, and measure the diameter, then straighten the string you will see that the “crust” is much longer than the diameter you have already. Diameter is one one parameter of a circle,but we can use it with other formulas to get useful information. 2 12 inch pizzas is not 24” of pizza- the total amount of pizza is far greater. You have to look at all 3 dimensions when making the comparison, and account for total areal.
Doubling the 12 inches would give you a working diameter of 24 inches. You double pi because you are calculating for 2 12 inch circles and not one 24” circle. No joke. This is true.
Typically, though, people are more particular about how to share it out. If you do the typical 8 slices, then you get 16 slices from the 12" and only 8 from the 18". Plus, you get a better crust to body ratio with the 12".
Better is subjective- but some people may prefer the crust ratio, the sizes of a slice, or the fact their are more. Having more than 1 pizza can make things like ordering a variety easier. A half/half may not be offered, or you may need 2 half half pizzas- meaning you can easily have 4 combinations of toppings with 2 mediums vs 2 with one large. You may have a situation where kids and adults are getting pizza and in different rooms or at different tables, and don’t forget if you want a specific combination of toppings- the extra topping charge is usually higher on a large than a medium, so while you get more pizza you can easily get less toppings with the large. By the numbers a single large will yield more pizza for less per square inch in cost. However the individual situation may not favor it. For example a single split pizza is harder to do 1/2 one type or quantity of sauce and another if one wants a bbq sauce, or white sauce, etc. the middle slices may end up a disgusting hybrid.
Or is this the joke and I'm not seeing it?