Doing Quick Calculations in a spreadsheet e.g. number of staff, average salary
Building spreadsheets can be an iterative process. You will often see spreadsheet jockeys working with their calculators and checking their numbers. You are continually checking and rechecking that the numbers make sense.
There are a number of built in tools that help you with this. We find we use these simple tips and tricks continuously and it is a good idea to learn them now