If a "chunk" of a football game is defined as 18 minutes, then after 36 minutes, or two chunks, there will be 6 commercials. 3 chunks is 54 minutes, so 48 minutes falls short by 6 minutes. If a chunk can be split, there would be one commercial every 18/3=6 minutes. So in 12 minutes (48-36) there would be 2 commercials. In total, then, we have 3+3+2=8 commercials or 3+3+3-1=8.