May 12th, 2018, 07:08 AM  #1 
Newbie Joined: Apr 2018 From: India Posts: 6 Thanks: 0  Short Trick Number System
Hello friends , you can learn a lot in 3 minutes 
May 12th, 2018, 07:27 AM  #2 
Math Team Joined: May 2013 From: The Astral plane Posts: 1,797 Thanks: 715 Math Focus: Wibbly wobbly timeywimey stuff. 
Part of my problem is that I don't speak the language and can't follow it. An example of my problem is this: At 0:36 the video seems to be claiming that says $\displaystyle 656 \times 838 \times 972$ is somehow 6? My guess is that we are looking to find the last digit in the multiplication? Dan 
May 12th, 2018, 08:10 AM  #3 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,421 Thanks: 832 
This post (which is your 2nd post) is as useless as your 1st post...

May 12th, 2018, 03:12 PM  #4 
Senior Member Joined: May 2016 From: USA Posts: 1,030 Thanks: 420 
Subscribe. Spam. Ban the jerk.

May 12th, 2018, 07:19 PM  #5 
Newbie Joined: Apr 2018 From: India Posts: 6 Thanks: 0 
This video is a trick to find unit digit of very big multiplications.

May 13th, 2018, 09:22 AM  #6 
Senior Member Joined: Aug 2012 Posts: 1,889 Thanks: 525  
May 13th, 2018, 09:55 AM  #7 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,421 Thanks: 832 
...and why d'hell is "very big" scary? You really end up multiplying a few digits. Plus no multiplication required if one or more of those last digits is 0 or 5. 
May 13th, 2018, 07:18 PM  #8  
Newbie Joined: Apr 2018 From: India Posts: 6 Thanks: 0  Quote:
Watch it complete you will understand  
May 13th, 2018, 07:18 PM  #9 
Newbie Joined: Apr 2018 From: India Posts: 6 Thanks: 0  
May 13th, 2018, 11:54 PM  #10  
Senior Member Joined: Oct 2009 Posts: 403 Thanks: 139  Quote:
It states that if $a$ is not divisible by $2$ or $5$, then the last digit of $a^4 = 1$. Thus for example, to compute $$333^{4323133}$$ we write $4323133 = 4*1080783 + 1$ Hence in mod 10 $$333^{4323133} = (333^4)^{1080783}333 = 333 = 3.$$ Isn't this a lot easier????? Now if $a$ is divisible by $5$, then the last digit of $a$ is always $5$ or $0$, and it is easy to see which. If $a$ is divisible by $2$, then use that the last digit of $2^5 = 2$. Last edited by Micrm@ss; May 14th, 2018 at 12:05 AM.  

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