## Welcome to BrainDen.com - Brain Teasers Forum

 Welcome to BrainDen.com - Brain Teasers Forum. Like most online communities you must register to post in our community, but don't worry this is a simple free process. To be a part of BrainDen Forums you may create a new account or sign in if you already have an account. As a member you could start new topics, reply to others, subscribe to topics/forums to get automatic updates, get your own profile and make new friends. Of course, you can also enjoy our collection of amazing optical illusions and cool math games. If you like our site, you may support us by simply clicking Google "+1" or Facebook "Like" buttons at the top. If you have a website, we would appreciate a little link to BrainDen. Thanks and enjoy the Den :-)
Guest Message by DevFuse

# Rolling a coin part 2

3 replies to this topic

Senior Member

• Members
• 1664 posts
• Gender:Female

Posted 03 June 2013 - 03:55 PM

Hopefully I don't ruin the question  this time.

Assume that we have two coins that are not identical in size but are both perfect circles. We want to roll a coin along the edge of another coin where the moving coin starts at 1 side and ends up on the exact opposite side (only traveling half of the non-moving coin) and still end up in the same starting position (the moving-coin's orientation ends in the same position it started).

What size(s) must the moving coin have relative to the non-moving coin?

If we want the moving coin to travel 3/4's around the non-moving coin and still end up in its starting position, what sizes for the moving coin work?

• 0

### #2 k-man

k-man

• Members
• 439 posts
• Gender:Male

Posted 03 June 2013 - 04:21 PM

Spoiler for first part

Need more time for the 3/4 case.

• 0

### #3 Barcallica

Barcallica

• Members
• 135 posts
• Gender:Male
• Location:Room with a View

Posted 04 June 2013 - 06:04 PM

Spoiler for first part

Need more time for the 3/4 case.

isn't it any even number?

• 0

### #4 Barcallica

Barcallica

• Members
• 135 posts
• Gender:Male
• Location:Room with a View

Posted 04 June 2013 - 06:07 PM

Spoiler for for 3/4

• 0

#### 0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users