Guess it depends on what level you're trying to enter - I interviewed with five relatively big name firms in London, did well, and know absolutely nothing about accounts and NPV - some intuitions at best. This was for associate/junior consultant roles with R. Berger, PwC, Marakon, etc. Common sense and business awareness with a bit of structured thinking seemed much more important. Was happy I'd practiced case studies, though. Suspect if you're post-MBA it's a different story? Best of luck!