Good knowledge of math:
- A quick approximate count (how much money did we spend if the 1st server shows an expense of $325, the 2nd shows an expense of $512, and the 3rd shows $187?)
- A good understanding of percentages (what will the ROI become if it was 50% before and revenue drops in half?)
- Basic combinatorics and probability theory (what is the probability that a roll of 2 dice will result in a total of 7?)