10 + Pins in Row 5 = 15
The total number of pins in a triangular arrangement is called a triangle number.
The total number of pins in a triangular arrangement of 5 rows is 5 plus the
total number of pins in 4 rows.
Let us call this number Triangle(5).
The chart gives the first seven triangle numbers.
But it seems not to be complete. Fill it in as you
click on the picture to see each arrangement of
Triangle(N) pins.
| Triangle Numbers | ||
|---|---|---|
| Rows | Triangle(Rows) | Formula |
| 1 | base case | |
| 2 | 2 + Triangle(1) | |
| 3 | 3 + Triangle(2) | |
| 4 | 4 + Triangle(3) | |
| 5 | 5 + Triangle(4) | |
| 6 | 6 + Triangle(5) | |
| 7 | 7 + Triangle(6) | |
Fill in the chart.