Multiplication table is one of the first things kids learn at school. However, 9x9 is the upper limit of the table and other multiplication operations are supposed to be done on paper, in memory or ... by means of the omnipresent computer technology. However, you will notice that by memorizing the table up to 20x20, your multiplication skills will grow dramatically. And memorizing 20*19/2 combinations is a piece of cake with SuperMemo.
Do you know the example situation that took place in one of the American supermarkets in 1998. When the supermarket was hit by a power failure, and all checkouts were out of order, nearly all checkout ladies had problems with ... multiplication table!
Now, at the door of the 21st century, when simple mental calculations have been replaced with computers, we no longer feel a burning need to be able to fluently multiply. Once you master our collection, you will discover a number of situations in which the ability to make quick calculations becomes very useful.
Please note that this collection should not be just memorized! Please try to follow the mental path of derivation in which you build upon the 9x9 table. Your only grading criterion should be the immediacy of your response. If your thinking is not satisfyingly immediate, grade yourself Bad or Null. For example, instead of memorizing that 7x16 is 112, you should note that 7x10 is 70 and 7x6 is 42 and that 70+42 is 112. That is the shortest path to quickly mastering this collection and getting a boost in mental computation skills.