In a certain chemical, the ratio of zinc to copper is 3 to 16. Ajar of the chemical contains 800 grams of copper. How many grams of zinc does it contain?
It contains grams of zinc.

For this, you will need to know the triangle numbers. To know how many are on row ten, find the cumulative frequency (running total) of every number up to ten

1 = 1
2 = 3
3 = 6
4 = 10
5 = 15
6 = 21
7 = 28
8 = 36
9 = 45
10 = 55

If there are 55 containers and 29 are knocked down, we do
55 - 29 = 26
26 containers remain