Thursday, September 5, 2013

Lucky number 9

Remember when I (tried to) participated in Blog Every Day in May? Well, I've just learned that Jenni is hosting another month of blogging prompts & link-ups, this time called Blogtember. I had such a good time with the prompts (that I kept up with) last time, that I've decided to jump on the wagon again. Yes, I'm already a few days late (typical - remember the name of this here blog??), but I'm diving right in and going to do my best to keep up! Off we go :)

Thursday, September 5: Pass on some useful advice or information you learned and always remembered. 

I tossed around many "deep" lessons I've learned and pieces of advice for having a rich, wonderful life... and then I threw that out the window and decided to go with something actually useful.

I have always been bad at math. It's a fact. For me, numbers just do not make sense. I've accepted it, and I've learned that there are lots of tricks out there to help with some of the basics. These have been key to my math success (right up until I failed Calculus in 12th grade.... whoops. Actually, they let me drop after the drop date so that I didn't have a big ol' red F on my beautiful report card... sigh of relief!). Anyway.

Here's a trick I learned in 2nd grade, and literally still use to this day: How to multiply by 9.

Example: 9 x 5 = ???

When multiplying by 9, take whatever number you want to multiply (5) and subtract one (now it's 4). That's the first digit in your answer.

Example: 9 x 5 = 4___???

The second digit in your answer is whatever number adds to the first number to make 9 (that would be a 5).

Ba-da-bing, ba-da-boom, there's your answer!

9 x 5 = 45!

We win!

This really does work. Look:

  • 9 x 8 = 72 (7+2 = 9)
  • 9 x 6 = 54 (5+4 = 9)
  • 9 x 2 = 18 (1+8 = 9)

Granted, this only works when multiplying single digits, but it's still very useful. Amiright?! All you lovely blog readers will now always know how to multiply by 9s. You're welcome.

Do you have any useful advice or information to pass along? Is it deep, or something handy?

2 comments :

Rachel said...

Maths was never my strong point at school! We used to learn our times tables by chanting them in a morning. But long division till scares me!! :-)

blm said...

never learned this trick! i'm totally going to use it to impress LB when she gets to multiplication. ;)