FWIW I just tested this with GPT4 and it seemed to get it correctly.
Prompt: I have a duck, some grain, and a fox. I'm at a river crossing and I can only take one of them with me on the boat at a time, leaving them on the other side and coming back to get the next. I can't leave the duck with the grain, or the fox with the dock, because the predator will eat its prey. In which order should I get them all across?
GPT4: To get all of them across the river safely, follow these steps:
Take the duck across the river.
Go back to the original side, empty-handed.
Take the grain across the river.
Bring the duck back to the original side.
Take the fox across the river.
Go back to the original side, empty-handed.
Finally, take the duck across the river again.
Now, all three - the duck, the grain, and the fox - are safely on the other side of the river.
Prompt: I have a duck, some grain, and a fox. I'm at a river crossing and I can only take one of them with me on the boat at a time, leaving them on the other side and coming back to get the next. I can't leave the duck with the grain, or the fox with the dock, because the predator will eat its prey. In which order should I get them all across?
GPT4: To get all of them across the river safely, follow these steps:
Take the duck across the river.
Go back to the original side, empty-handed.
Take the grain across the river.
Bring the duck back to the original side.
Take the fox across the river.
Go back to the original side, empty-handed.
Finally, take the duck across the river again.
Now, all three - the duck, the grain, and the fox - are safely on the other side of the river.