Logic

Here's the math problem.

Kate is stringing a necklace with 9 beads. She wants to string the same color for the first and 9th bead. Another color for the 2nd and 8th bead and so on. Will there ever be 2 beads of the same color next to each other on the necklace? How did you figure this out?
I believe the exercise was to discover that 9 is not a multiple of 2 and therefore there could be no beads next to each other.

However firstborn looks at things a little deeper.

He kept telling me that there would be two together. So I asked him which two.

His response, beads 1 and 9.

It took me a minute to figure out that he had already tied the necklace ends together in his mind. I mean after all, it's a necklace. You will tie it together in the end, right? And when you do, there will be bead 1 and bead 9 right next to each other. She didn't say anything about the knot in the middle.

I told him to put down both answers.