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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.)
 7 ways | Comment 5 of 14 |

3 moves:

6  1  2  9
3  4  5
7  8

4 moves:

2  3  4  5
6  7  8
9  1
0

6 moves:

6  7  8  9
3  4  5
1  2
0

7 moves:

2  0  1  3
5  4  6
9  7
8

8 moves:

0  1  2
9  3  4
6  7
8

9 moves:

6  7  8  9
3  4  5
1  2
0

10 moves:

9  8  7  6
2  1  0
4  3
5

5 moves can't be done without exchanging a coin so really it doesn't work.

 Posted by Lisa on 2005-08-15 09:04:48

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