Question #b3e6b

1 Answer
Sep 14, 2016

103 toothpicks in the 50th figure.
2n+3 toothpicks in the 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 1st figure has 1 toothpick in the top row and 2 in the bottom row, that means that the nth figure will have n toothpicks in the top row and n+1 in the bottom row. Adding these to the 2 toothpicks which constitute the left and right sides, we get the total for the nth figure as

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

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