Question #b3e6b

1 Answer
Sep 14, 2016

103103 toothpicks in the 50^"th"50th figure.
2n+32n+3 toothpicks in the n^"th"nth figure.

Explanation:

In each progressive figure, one toothpick is added to the top row and one is added to the bottom row. As the 1^"st"1st figure has 11 toothpick in the top row and 22 in the bottom row, that means that the n^"th"nth figure will have nn toothpicks in the top row and n+1n+1 in the bottom row. Adding these to the 22 toothpicks which constitute the left and right sides, we get the total for the n^"th"nth figure as

n + (n+1) + 2 = 2n + 3n+(n+1)+2=2n+3.

To figure out how many are in the 50^"th"50th figure, then, we just let n=50n=50 to get 2(50)+3 = 1032(50)+3=103.