I've got to admit that my "old school" math skills are in a pitiful state... most likely because it's been a long time since I've had the need for them.
And, thinking back, I was never very "focused" in math classes at school... and, I've never used a Slide Rule in my life.

Get past anything really basic, and I am totally "Calculator Dependant" ... I should probably spend some time re-learning some math skills.