75% feels right. If the answer had been anything outside of 65%
  - 80%, I would've been surprised. I deal with estimations all of
  the time, and it's important to be able to come up with ranges
  of potentials rather than exacts.

  Is it math? Probably, but don't ask me to show my work. I hated
  showing my work because that kinda ruins it. It's more like
  visualization rather than the scribblings of 18th century
  madmen.