I was asked yesterday, why do they teach the multiplication tables in school. Wasn’t sure whether this was common knowledge, but here’s how it goes. Once you know how to multiply the numbers from 1 to 9 with each other, you can multiply basically any two numbers by hand; doesn’t matter how many digits they have.
Let’s say you want to multiply 132 × 18. When you learn your times-tables, these numbers are not covered. But there is a method for you to follow that will just involve multiplying numbers less than 10. It does assume that you know how to add, but learning how to add numbers with several digits is not that hard either.
There’s more than one way to do multi-digit multiplication, but you can find the descriptions here: https://en.wikipedia.org/wiki/Multiplication_algorithm.
Of course, youtube has a few demonstrations too, for example:
So, 132 × 18 = 2,376. You would be multiplying these numbers on the way: 2 × 1, 3 × 1, 1 × 1, 2 × 8, 3 × 8 and 1 × 8 (which are all really simple!)
Now if you ask why to learn how to multiply numbers in the first place? I find mulitplication comes up quite a lot just in ordinary tasks, doubling baking recipes, find distance from velocity and time, and vice versa, buying quantities of various items. Sometimes I use a calculator, or spread sheet, but often it’s good to do without. There’s lots of different applications!