I love numbers. I think they can be a lot of fun. When I was learning how to multiply and then teaching others, I learned several different tricks to help you remember the multiplication facts or find out if a number was a multiple of another. My favorite ones involved the number nine.
If you had up the digits of any number and the sum is nine, then the original number is a multiple of nine. I have no idea how that works, but it does.
Also, if you are multiplying by nine, you have the answers right on your hands. Hold out both your hands and hold out your ten fingers. Then, if you are multiplying by say, three, you hold down the third finger from the left. That would leave two fingers up to the left of that finger and seven fingers up to the right of that finger. So for 9×3 you get 27. They’re even in place value order!
When you teach kids that trick it’s fun to then watch them casually use it during class. It’s something they’ll never forget.
I am an educator and PhD. I quilt, belly dance, run, read, and try to grow things. I am a Mormon. I am infertile. I am a daughter, sister, aunt, grand-daughter, friend, wife, and mom.
Brett L. Dennis
Mama g
Giggles
AmandaStretch
that’s so true, cuz i totally remember that from grade school! i use the sum of numbers is divisible by nine rule all the time for my new favorite number game, kenken. man, i’m such a geek.
… and when you teach it to adults, you can have fun watching them casually use it during boring department meetings.