system
A chat on subreddit /r/me_irl
human
The extra 2 inches of a 15 inch pizza equals 33.1% (or one third) of a 13 inch pizza.

This means he is missing 25% of his total advertised pizza area.

Source: πr^2
gpt
r/theydidthemath

Had to scroll far too long to find this, this is actually a huge difference. And you can’t just say it’s the same mass and call it a day, it’s a different product then because the bottom gets thicker.