This is a fun one because it illustrates that you failed the test just like I did.

Reread carefully: the question compares "a kilogram of feathers or a kilogram of feathers".

I've never heard that one before but my brain pattern matched right over to "a kilogram of feathers or a kilogram of steel" and moved on. I had to read it 3 times before I got the subtlety.

It's a trick trick question.

It's meant to appear as the often used trick question comparing different densities of materials but OP says feathers twice.

The trick is that an LLM will add in a dense material to the answer because it's only ever seen the question asked that way.

I wouldn’t even say it’s failing. Recognizing and correcting obvious errors in speech is a feature not a bug, both in humans and LLMs. Is it more likely that they meant to say feather twice or they mistyped?

not 'super intelligent' humans who are familiar with this old dad joke :)