Point to the number that is NOT the 9. Step Two: Subtract 1 from the number that you are pointing to. Step 3: When you add the numbers in the product together, they will make 9. As you can see, this works with any basic multiplication fact involving a 9.
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Notice that in every case, the sum of the numbers in the product add up to 9! Would you like a free poster and activity sheet for this strategy? Check out my detailed blog post with lots of pictures HERE. This was awesome!! I tried it with a struggling student last week.
Math Forum: Ask Dr. Math FAQ: Learning Multiplication Facts
It really works!!! Thanks for sharing Shelley!!! I always knew in my head it was not appropriate to teach the finger trick, but was at a loss for a better way. You found it!!!! Love this.
Wish I knew about this when I was learning. Thank you so much. This is a good method but involves too many numbers and a relatively complex calc which prevents it from replacing memorization. This method is so fast — and it is a calculation. Almost instant because the two ops are on the same number:. If you add up how far the two numbers are below , you can subtract that new number from to get your first two digits. Then multiply how far the numbers are below , and you get the final two digits. If you need to multiply a two-digit number by 11, you can use this trick if the sum of its digits is under Just add the two digits together, then place that inside the two digits, and the answer magically appears!
Have a kid who's being introduced to fractions?
Using Legos can help make learning about fractions much more fun for a child. Okay, and for adults too. You probably know you can add on your fingers, but you can also multiply on them; in particular, when you are multiplying numbers by each other. For this, think of the fingers on each hand as being 10 through 6.
Then have the fingers of the two numbers you're multiplying touch each other in this example, it's 7x8.
How the Simpsons (And You) Can Multiply by Seven Using Your Fingers
The number of fingers above the intersection is 5. The number of fingers at or below the intersection is 2 times 3, or 6. Put those numbers together and you get Sound complicated?
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Go here to see it in more detail. This is an alternate way to multiply two numbers together. In this example, 12 is represented by the black lines one line, then two more , and 13 is represented by the blue lines one line on the bottom, then three more on top. Once you have your lines, count the number of spots where the lines intersect, and you get your answer. It can be easy to mix up the "greater than" symbol with the "less than" symbol. If you have trouble keeping them straight, you can think of the symbols as alligator mouths.
The alligator will want to eat the number that's bigger, which is why the top alligator is the "less than" symbol, and the bottom one is "greater than. This is another version of the age trick mentioned earlier. When you multiply 7, 11 and 13 together, you get So when you multiply by any 3-digit number, that number will repeat itself. If you need to multiply something by 15, here's a simple way to do it in your head.
And if you want to multiply by 20, just add a zero to the number, then double it.
If you weren't aware of this trick before, knowing how much to tip at a restaurant just got a lot easier. And here's another one that might not actually be beneficial in the real world. But if you ever want to make a bar bet that you can calculate ,, squared without using your calculator, you can totally win. Latest Fails Funny News Awesome.