Question

Mari has 28 wooden cubes. She want to stack them to form a triangle. Each row will have one block fewer than the row below it. How many blocks will be on the bottom of the pyramid?

Answer 1

7 blocks will be at the bottom :)

Hope I helped :D

Answer 2

7 cubes.
imagine that ∆ are the blocks, it should be something like this:
∆
∆∆
∆∆∆
∆∆∆∆
∆∆∆∆∆
∆∆∆∆∆∆
∆∆∆∆∆∆∆
Add up everything 28 comes.