How to multiply anything by 5 - divide that number by 2, than move the decimal one to the right. It’s a dumb little trick, but I thought of it when I was in 2nd grade or something, and am still proud of it

If you take a number and multiply it by 9, then put down that finger on your hand (going left to right from left pinky), if you count the number of fingers on the left of that finger as the 10s place, and the number on the right as the 1’s place you can determine what nine times any number is!

This assumes you have all your fingers…
You should have put down you left ring finger (2nd finger from the left), leaving your left pinky on the left (1 in the tens place), and then the remaining 8 fingers on the right: 18.