In school, you probably had to memorize your times tables through ten or twelve. Now, some schools are requiring your times tables memorized through twenty. However, there is a cool method that can make you multiply these numbers instantly in your head, so quick that it seems like you've memorized them! And you didn't!!
Let's take a simple one, 12 x 13. You may know this one to be 156, or already punched it into your calculator. However, we will try to do it anyways. First, you have to add the last digit of the second number to the first number. 12 + 3 = 15. Next, we tack a zero onto this sum to give us 150. Finally, we multiply the two last digits of your number. 2 x 3 = 6. We add this product onto the number we had earlier (150) to give us 156, exactly what we said.
Let's try a bigger one: 18 x 17. First, you add the 18 + 7, the last digit of the second number, to get 25. Then, we tack on a zero to get 250. Finally, we do 8 x 7 = 56. Add that to 250 and you get the answer of 306, which is the correct answer.
With a little bit of practice, you will be able to multiply these numbers faster than a calculator! Isn't that cool?!