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 Inverting Triangles (Posted on 2005-08-15)
A piece of paper had the following diagram:
```               o              o o o o
From:   o o         To:  o o o
o o o              o o
o o o o              o
```
Below it, it read "Given the initial formation of ten coins, move exactly # coins to produce the end formation." It was pretty obvious that # stood for a digit, but it was smudged and couldn't be read. What possible numbers could it have been so the problem was solvable?

To allow explaining the solution, number the coins like this:

```           0
1 2
3 4 5
6 7 8 9
```
Note: This problem was inspired by a forum question by Nicole.

 No Solution Yet Submitted by Erik O. Rating: 2.1667 (6 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
 re(2): 7 ways - your rules | Comment 7 of 14 |

Good point. Can we start rolling coins, say starting with 6, to form the "to" shape off of the 9? In this case, the 6 would end to the right of 9 and would be the left most corner of the "to" shape. We should peel the coins off and on to avoid the trapped coin/space issue, and finish with the 9 rolling to the last new spot. How does this sound?

 Posted by owl on 2005-08-15 15:23:34

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