#### Thread man

##### Well-Known Member

I posted a thread with the title

**Mathematical Question**. In the first post I wrote:

*“I've always regarded myself as being good at geometry (and trigonometry) and I suppose you have to be working with threads. However, and to my surprise, I got the wrong answer to this and I even regarded it as simple!*

Use your head or pencil and paper but don't cut anything out. That'd be cheating ☺

How many revolutions of the small circle (R1) will it take to circle the circumference of the large circle (R3) to arrive back at the starting point?

Any answers?”

Use your head or pencil and paper but don't cut anything out. That'd be cheating ☺

How many revolutions of the small circle (R1) will it take to circle the circumference of the large circle (R3) to arrive back at the starting point?

Any answers?”

That was, or so I thought, a simple instruction. Already in the second post was an incorrect answer and the same as I’d arrived at when I saw the video on Youtube. Then things got “interesting”.

I don’t know what to say to post 3. The 5th post gave the Youtube video where I saw the question. To me posting that spoiled everything as I could just as well have posted that video myself from the beginning.

All of this reminds me of when I was at school and the teacher said he had a test for us. We were all given 3 sheets of paper with what appeared to be relatively simple questions and a line under each question where the answer could be written.

The first sentence was

*“Read the paper carefully before answering any questions”*. Anyone doing that would have arrived at the last sentence that stated

*“Don’t answer any questions and simply initial the paper on the top right hand side of the first page and return to me.”*

In a class of 25 how many returned the paper with only their initials on it? Not one!

Getting back to the original thread it still fascinates me that the answer is always the Pi D equation + 1. Two identical diameter circles 1 + 1 and the answer is 2, 3 to 1 and the answer is 4 and the stationary circle, even if 15 times the diameter of the small circle is 15 + 1.