In school we are all made to learn tables of upto 10. As a kid, I realised I didn't need to memorize the tables and I could just add one number of the same to get the next value. So I didn't memorize any table after 6. Teachers were pissed. They insisted that I had to memorize them. But I'd act like I was trying to recall the value from memory, while actually adding it in my head. The slight downside is that I still don't know the tables of 7, 8 and 9. But that does not stop me from doing mental calculations. When I have to do 7x6, I reverse it and recall 6x7. And if I have to do 7x7, I use 6x7 and add a 7 to it. The thing is, these are arbitrary conditions that we have imposed on ourselves. In the real world, there is no limit on what method to use to get a particular solution. You can use whatever method you want. And shortcuts teach you how to do things quicker. This method taught me to do multiplications indirectly. the average person is sometimes impressed when I calculate something like 52x24 in my head in a few seconds accurately. But it's really simple. Instead of calculating it directly, I calculate simpler numbers: 50x24 and 2x24, and then add them up Years of education, dumbs you down to do things in specific ways to obey these arbitrary self-imposed rules. To do things by the book even when the book is badly written. But you've got to break free from these constraints that exist nowhere except in the imaginations of people. In a world that forces you to dot the i's and cross the t's, do what you want. Cross the i's and dot the t's.