The Ploughman's Puzzle

Sixteen (16) trees are planted in a triangle shape of twelve (12) rows with four (4) trees in every row. How can the 16 trees be replanted to make 15 straight rows, with 4 trees in every row?

Note: There can be several solutions to this puzzle.

This puzzle is based upon a historic Canterbury Puzzle. Why is this puzzle named The Ploughman's Puzzle?

The origins of this interesting puzzle comes from an old publication entited "The Project Gutenberg eBook of Amusements In Mathematics, by Henry Ernest Dudeney" and adapted it to my images.

ploughmans puzzles
ploughmans puzzles