This week we posed puzzle is based on logic, rather than maths or words. Once again it looked easy, but it is harder than it first appears.
Arrange six pennies (or any other coins of the same size) into a triangle; three coins on the bottom row, two in the middle row, and one on the top. By moving the coins one at a time, make a straight line of six coins. Easy!
However, there is one extra stipulation – at the end of each move the coin that you have just moved must be touching two other coins. Not quite so easy!
The trick is realising that, as the last coin moved has to touch two other coins, it can not go on an end. So it must go in a gap between two coins, and you need to have a row of three <gap> row of two just before the final move.
Consider the six coins with the top coin numbered 1, the second row numbered 2 and 3, and the third row numbered 4,5 and 6. All numbered left to right.
The notation below is A -> B,C means move coin A to touch coins B and C.
1->2,4
3->1,4
2->1,3
4->2,3
1->2,4
2->1,4
1->3,5
Seven moves, but is that the shortest solution?