Mathematician demonstrates useful multiplication trick that nearly nobody knows
Multiplication is a memory-based skill. But just taking the time to memorize it will save you a ton of trouble.
Though there will still be those moments when you want to have physical things to help visualize the math.
Well, good thing you have fingers.
If you ever need a visual aid, just count on your fingers for help. No pun intended. Thanks to the magic of math, you’ve actually got a simple way to multiply the numbers 6 through 10 with your fingers.
It’s as easy as turning your hands. No, seriously. First things first, consider the numbers 6-10 represented by your fingers starting from the thumb. So your thumb is 6, then the pointer is 7, the middle finger is 8, the ring finger is 9, and pinky is 10.
This goes for both hands.
With that in mind, to multiply any number from 6 to 10, all you’ve got to do is rotate your hand so the corresponding finger (that represents the number you’re multiplying) points to the second “number” on your other hand.
Now, including the two fingers that are touching, count the total number of fingers on the bottom end of your hands.
This will be the tens place value of your answer. So if you’re multiplying 7×8 and thus have your two pointer fingers touching your other hand’s middle finger, you’ve got a total of 5 fingers (your two pointers and thumbs plus the middle finger) to represent 50.
Next, take the remaining number of fingers on your right hand and multiply it by the number on your left. In the case of 7×8, having your pointer on your middle finger leaves 3 fingers free on the right and 2 on the left. So 3 x 2= 6.
Add that to the previous number to get the answer.
In this case, the answer is 56, which is correct!
Let’s take the problem 6 x 9.
We rotate our hands so that our thumb (since it represents 6) touches the right hand’s ring finger.
That makes 5 fingers on the bottom, including the thumb and ring finger that represent 7 and 8. So we’ve got 50. Alright, what’s next?
We’ve got 4 free fingers on the left hand and 1 free one on the right.
Since 4 times 1 is 4, we add that to the 50 to get 54.
See? It works.
Now when a quiz is inevitable or you’ve got to count change or expenses, you have fewer problems on your hands. Again, no pun intended.
Of course, this doesn’t mean you shouldn’t memorize your multiplication tables. In most cases, nothing beats knowing it by heart. Plus, this only works for six to ten anyway. Yes, you do have a calculator handy on your phone 24/7 but it’s not exactly a memory-building tool, is it?
And you don’t need me to tell you that those aren’t allowed during quizzes.
Some schools might allow calculators on certain days. The idea of allowing calculators in class is a lot more nuanced than you’d think. After all, you do need them to check your answers, right?
At least you have another reliable way to multiply six through ten now! I wonder how many moments in our lives would’ve been easier had we known this.
Watch the video below!
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