Tuesday, November 17, 2009

WFMW -- multiplying by nine

Keeping learning fun and active are always a part of the game, especially with the younger set. We have a few "hand games" that help us with memory work at various times.

We have a simple trick in our house for learning and remembering your "9 X ___"

Many of you may already know this, but if you don't this is a life saver. My kids easily master their times tables up to five, and then yawn through the tens, but six through nine present a bigger challenge.

Here is how we make the nines as easy as pie, too:

Place both hands on the table in front of you. Placing them, rather than holding them up keeps kids from flipping them around and making this more difficult later on.

Whatever number you need to multiply by nine, put that finger down. For example, if you are multiplying by seven put down the seventh finger from the left:

Then, you start on the left counting the fingers that are up by tens, and when you get to the finger you tucked under you switch to counting by ones. I compare this to counting by dimes and pennies if my kids get mixed up. So, 9 times 7 is 63.

When first learning this method it helped to skip count by nines while switching which finger we tuck under. I didn't do this step with my first couple and it took them longer to catch on to the concept. With my third child I started with skip counting along with the fingers and the transition to the nine times tables with her was more seamless, and she is almost done relying on them altogether.

Another handy memory tool that relies on our hands is how many days there are in each month of the year. Using one fist and the pointer of the other hand you say the months of the year while touching the knuckle, then the valley between. So, January (31) gets the first knuckle, February the valley (28-29), March (31) back on a knuckle, April (30) into the valley, and so on.

It works out perfectly that you get to the last knuckle on "July" which sends you back to the first knuckle for "August," both of which have 31 days.

Before learning this trick (sometime in high school . . .) I used to go by the rhyme, "30 days hath September, all the rest I can't remember." Which obviously did me very little good.

Have any other great memory tools using fingers or other tricks that you would like to share?

Looking for more inspiration to make your life easier in a variety of realms? Check out Works for Me Wednesday for lots of great sanity-saving tips.


Becky @ Our Sweet Peas said...

Ha, I can never remember the rest of the rhyme either. I've heard the knuckle thing before but am glad to be reminded myself b/c I always forget. Thanks!

Jenny @ Just Jennifer said...

That's pretty nifty. I still have trouble multiplying, as sad as that is. I never really got the hang of it (learning disorder). This is really helpful though :D Thanks for the tip.

jmberrygirl said...

My husband taught me a little trick to "check" multiplication by nines. The products can be added to equal nine. For example, 7 X 9= 63 and 6+3=9. 8x9=72 and 7+2=9... and so on.

Becca @ Our Crazy Boys said...

This is the only thing that works for our 9 year-old. What a great tip to share!