Robert will be using an arithmetic series to find the total number of cans.

This is because the number of cans decreases by 1 for each subsequent row, forming a sequence with a constant difference between the terms. The total number of cans is the sum of these terms, which is characteristic of an arithmetic series.

Would you like a step-by-step breakdown of the calculations for this pattern?

Here are 5 questions related to this problem:

1. What is the formula for the sum of an arithmetic series?
2. How many cans are there in the 4th row?
3. How would the total number of cans change if Robert stacked 9 rows instead of 7?
4. How is an arithmetic sequence different from an arithmetic series?
5. What is the difference between a geometric and arithmetic sequence?

Tip: In an arithmetic series, the common difference between terms is always constant.