Mark wants to build a pyramid of soda cases that's four levels tall. Each level of the pyramid has a square base where each side is one case longer than the level above it. The top level is just one case. How many cases of soda does Mark need?
We know that the top level just has one case. Since each level has one more case per side than the level above it, the second level has sides that are 2 cases long.
We can figure out how many cases we need for the second level by finding the area of a square with a side length of 2: 2 cases * 2 cases = <<2*2=4>>4 cases
The third level has three cases per side, so we need to find the area of a square with side length 3: 3 cases * 3 cases = <<3*3=9>>9 cases
The fourth level has a side length of 4, so we find its area with 4 cases * 4 cases = <<4*4=16>>16 cases
Finally, we add up the number of cases we need on each level: 1 cases + 4 cases + 9 cases + 16 cases = <<1+4+9+16=30>>30 cases
#### 30