The majority of today's office-based jobs require an understanding of numerical information (numbers, tables, charts) and the ability to rationalize them.
The data-analysis process often comes down to solving a simple linear equation to get the desired information.
Public questions (free account) are common interview questions. They are great for practicing, or if you want to filter candidates using the classic problems.
How old is John if, in 38 years, he will be 3 times as old as he is today?