Results 1 to 8 of 8
-
10th December 2023, 09:47 PM #1
The prize lies beneath - hidden in full view
- Join Date
- Oct 2010
- Location
- 1017m up in Katoomba, NSW
- Posts
- 2,453
A mathematical puzzle to solve...
Circle A is 1/3 of the radius of Circle B.Capture.JPG
If circle A revolves its circumference around the circumference of Circle B (which remains staionary), how many times will Circle A rotate on its journey? The circumference of a circle is 2 * Pi * r or Pi * Dia.
The same question, slightly rephrased, is posed in this picture (where Circle B remains stationary):
-
10th December 2023, 10:17 PM #2
GOLD MEMBER
- Join Date
- Aug 2004
- Location
- Brisbane
- Posts
- 767
The circumference of A must be 1/3 of B, so three revolutions. My backup answer is avocado green
-
10th December 2023, 10:20 PM #3
Butcher of wood
- Join Date
- Jun 2010
- Location
- Bundaberg
- Age
- 54
- Posts
- 160
??? Three ???
Using pi multiplied by D to get the circumference of each circle and that r = R/3 the two equations seem to cancel each other out with only “3” being left…
… but it is late, I’m practically in bed and I did that totally in my head so I’m probably wrong…Nothing succeeds like a budgie without a beak.
-
10th December 2023, 10:34 PM #4
SENIOR MEMBER
- Join Date
- Mar 2018
- Location
- Sydney
- Posts
- 28
I've heard this exact problem being discussed recently. Perfect timing!
The SAT Question Everyone Got Wrong - YouTube
-
10th December 2023, 10:36 PM #5
Senior Member
- Join Date
- Nov 2017
- Location
- Melbourne
- Age
- 73
- Posts
- 108
4. A does an extra revolution around its own axis of rotation in addition to its own circumference around B's circumference.
Circle Revolutions and the Coin Rotation Paradox
-
10th December 2023, 11:01 PM #6
GOLD MEMBER
- Join Date
- Aug 2004
- Location
- Brisbane
- Posts
- 767
super! Thanks, I never quite had a good explanation of a sidereal day but now I see it’s linked to this problem, makes it much easier to explain
Originally Posted by taz01
-
10th December 2023, 11:22 PM #7
The prize lies beneath - hidden in full view
- Join Date
- Oct 2010
- Location
- 1017m up in Katoomba, NSW
- Posts
- 2,453
That's where I saw it today. Thought y'all might like a puzzle. Originally Posted by taz01
-
11th December 2023, 12:35 AM #8
The prize lies beneath - hidden in full view
- Join Date
- Oct 2010
- Location
- 1017m up in Katoomba, NSW
- Posts
- 2,453
Just a footnote to this puzzle: one of the comments under the video said:
"Thinking about this yesterday and I realized the extra rotation becomes intuitive if you shrink the large circle down to a point, and rotate around that. Even though the diameter of the circle it's rotating around is zero, the "small" circle still has to make a full rotation to return to its starting point."
That's a great explanation!
Reply With Quote
Similar Threads
-
Older women solve problems
By Allan at Wallan in forum JOKESReplies: 1Last Post: 15th September 2011, 06:49 PM -
mathematical logic
By Calm in forum JOKESReplies: 1Last Post: 30th April 2009, 02:10 AM -
From a strictly mathematical viewpoint
By Munchkin in forum JOKESReplies: 0Last Post: 12th August 2004, 06:56 PM
Bookmarks