SOLUTION: Imagine that a triangle is formed with 10 pennies, as hsown below. By changing only 3 pennies, reverse the triangle so that it now points in the oposite direction. ......1 ...

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take the coins from position 7 and 10 and place them up on either side of 2 and 3........then take number 1 and place it below 8 and 9.......DONE

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Start with the given figure.


.......1
.....2 - 3
...4 - 5 - 6
7 - 8 - 9 - 10



Bring the 1 all the way down



.....2 - 3
...4 - 5 - 6
7 - 8 - 9 - 10
.......1



Place the 10 2 steps up (right above the 6)



.....2 - 3 - 10
...4 - 5 - 6
7 - 8 - 9
......1


Finally, place the 7 2 steps up (right above the 4)



7 - 2 - 3 - 10
..4 - 5 - 6
....8 - 9
......1



Now the triangle is pointing in the opposite direction.