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Interactive video lesson plan for: Two fast ways to multiply by 9

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► My Pre-Algebra course: https://www.kristakingmath.com/prealgebra-course

Here are two quick ways to multiply 9 by any number 1 through 10. If you’re currently in the process of memorizing multiplication tables, these are both great techniques to help you with your 9s.

For the first technique, you’ll use your hands. Hold out your hands flat in front of you, then number your fingers from left to right. If you want to multiply 9 by 1, bend down your first finger (the left-most finger). Then you count the number of fingers still up on either side of the finger you bended down. Because there are 0 fingers to the left of the bent one, and 9 fingers to the right of the bent one, then 9*1=09, or 9*1=9. Or let’s take 9*2. You bend down your second finger, which leaves you with 1 finger to the left of that bent finger, and 8 fingers to the right of that bent finger. So 9*2=18. And this works for multiplying 9 by anything 1 all the way through 10, because you can bend down your first finger, all the way through your 10th finger.

The second technique is a little more mathy. If you want to multiply 9 by 7, you start with the 7, and you subtract 1 to get to 6. And 6 is now your first number. To get the second number, add from 6 back up to 9. Since the difference is 3, the second number is 3. So 9*7=63. Take another example and do 9*4. Subtract 1 from the 4 to get to 3, and 3 is your first number. Add from 3 back up to 9. The difference is 6, so your second number is 6, which means 9*4=36.

● ● ● GET EXTRA HELP ● ● ●

If you could use some extra help with your math class, then check out Krista’s website // http://www.kristakingmath.com

● ● ● CONNECT WITH KRISTA ● ● ●

Hi, I’m Krista! I make math courses to keep you from banging your head against the wall. ;)

Math class was always so frustrating for me. I’d go to a class, spend hours on homework, and three days later have an “Ah-ha!” moment about how the problems worked that could have slashed my homework time in half. I’d think, “WHY didn’t my teacher just tell me this in the first place?!”

So I started tutoring to keep other people out of the same aggravating, time-sucking cycle. Since then, I’ve recorded tons of videos and written out cheat-sheet style notes and formula sheets to help every math student—from basic middle school classes to advanced college calculus—figure out what’s going on, understand the important concepts, and pass their classes, once and for all. Interested in getting help? Learn more here: http://www.kristakingmath.com

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QUORA // https://www.quora.com/profile/Krista-King

Tagged under: multiplying 9,multiply 9,ways multiply 9,techniques multiplying 9

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