How to Multiply by 9 Using your Fingers

April 9, 2012 by Lauren

This tip is so easy. It got me through 3rd grade, I used it in Calculus class, and I still use it while working at The Burlap Bag (who am I kidding, I rarely need math here at the shop! It’s fantastic!). BUT if I did need to multiply something by 9, I’d know it super fast.

First, you need to get in your head that your fingers (yes, including thumbs) are numbered from 1-10 starting on the left. Like below:

When you want to multiply 9 by a certain number, put that numbered finger down. So if you want to know 9×7, put down the “7th” finger.
Then count how many fingers are still up to the left of that 7th finger. There should be 6 fingers. That number 6 will be in the “tens” place.
Then count how many fingers are still up to the right of that 7th finger. There should 3 fingers. That number 3 will be in the “ones” place.

Place those two numbers together: 63. 9×7=63.

And you can do this from 9×1 all the way up to 9×10! (for 9×10, there will be 9 fingers up on the left, and 0 on the right. 90!)

Now you don’t need to struggle with remembering those multiplication tables for 9s. And it’s not even cheating, it’s just a helpful hint!

sidenote. We spent Easter afternoon at Zilker, and I decided to take the hand photos then. It’s ridiculously hard to be the hand model and the photographer. We decided I had the best hands to photo. Josiah has a huge blister from gardening. My friend Emily’s hands looked hilarious when she tried to put down just one finger. So I had to be the hand model. And the photographer. Except that I couldn’t click the button or even look through the viewfinder. Real serious issues, I know. 

Also, we later had issues with my camera remote. Apparently I had it set to a 2 second delay, which we figured out 5 minutes later. Always check your camera settings. We got this photo:
 Josiah: I can get it to work. Maybe if I put my arm up a little higher…
Lauren: I wonder how many Reese’s Easter Eggs I have left at home
Emily: Josiah, freaking give me that thing. Or I will punch you.

In the end, Em took the hand photos for me. And we had a great time at Zilker Park!
 (oh and forgive my hair. I’m just a hot mess. But check out that lovely Austin skyline in the background!)


5 Comments

  1. Teysha says:

    I am crazy about this post for a few reasons:
    1) I have realized I CAN NOT multiply anything above the 3’s. I have literally forgotten my entire math education beyond the third grade. HOW DID THIS HAPPEN. I BLAME ART.
    2) I have tried taking pictures of my own hands and yes, it is hard, and really impossible.
    3) Emily is there.

  2. Catherine says:

    My mother taught me this trick growing up, so handy! :P

  3. karla says:

    Or an even quicker way of multiplying by nine is to count back one by whatever you are multiplying by (ex: 9×7 so you would count back from 7 and pick 6) which becomes the tens number in the answer and then the second number is whatever adds up to 9 (6+3=9: so the second number would be three. Thus the answer of 9×7=63. I found this way faster than using my fingers.
    Also, for adding nine to a number (if it is a one spot number: 0-9) count back one from the number you are adding and then say teen…9+4 count back one from four; 3 so the answer is three teen…or thirteen. Works on eights by counting back two numbers. Anyhow I thought this was cool and thought I would tell you about it…cute blog by the way.

  4. Rebecca says:

    Well, I’m 55 and never knew either the hand trick or karla’s counting back trick. The hand trick is less “mathy.” I love it!!

  5. carlos says:

    i love this. i just found your blog and im going through it all. i literally just made your 2 ingredients banana cookies.

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