1. For example, the sequence 2, 6, 18, 54, ... is a geometric progression with common ratio 3.

2. The remaining formats fit in between all these formats, such that the sequence of formats A4, E4, C4, G4, B4, F4, D4, H4, A3 is a geometric progression, in which the dimensions grow by a factor 16√2 from one size to the next.