I'll never forget, from my photofinishing days, the impossible cropping requests.
People would see their 4x6 print of a group shot, and want an 8x10. But an 8x10 will cut off the sides of a picture because it's a different aspect ratio to a 4x6. You can decide what you want cut out, but you have to cut out something. Think about it. Double 4 inches, and you get 8 inches. Double 6 inches, and you get 12. Not 10. Therefore, if you want to see the entire picture you saw in your 4x6, you have to order an 8x12.
So this woman comes in, upset because in her 8x10, the people standing at the sides are cut out. I explained that she'd have to get an 8x12 to get them all in.
"Oh no, it has to fit into my 8x10 frame that I bought for this picture."
"Well then, you can either have the people at the edges cut off, or we can make the whole thing smaller but you'd have black lines above and below the image on the 8x10."
"Oh no, I don't want black lines. I want it to fill the whole frame."
"Well unfortunately you can't do that without losing the people at the edges."
"No, I want all the people included."
"Well I'm afraid you'll have to get an 8x12 and use a different frame."
"But I want to use THIS frame. That was the whole idea."
I can't tell you how many times I had similar conversations. I still am not sure why it was so hard to understand the concept of dimensions and also the idea that if you crop out the top, you also have to crop something off the sides.