@LSLGuy beat you to it with a similar approach upthread.
One of the things I’ve repeatedly found with ChatGPT is although it’s usually pretty good at solving problems like this – and often amazingly good at solving much more complicated ones – it usually misses obvious shortcuts, like in this case the fact that the room dimensions were an integral number of yards.
Here is a more involved example. To solve the problem, ChatGPT sets up a system of equations, solves them, and arrives at the correct answer. But as I realized when looking at the puzzle more closely later, the puzzle is actually simpler than it appears, but the AI couldn’t see the shortcut.