That's like the same as EasyCal! (glad2teach . co . uk)... except the easycal tricks go way on to...well...huger(infinite digits times infinite digits) multiplications mentally, and they were passed from ancient india 3000 years ago... so ha!
Pretty cool...the times 11 trick is well-known but I never quite applied until I saw it here.
The division by 9 trick I have never heard of but it is faster than long division for short numbers. I'm curious what is the proof of the division by 9 trick?
@orangegold1 Let n be an m digit number, whose digits are a_0, ..., a_{m-1}. First, note that 10 is congruent to 1 (mod 9). Hence, 10^k is congruent to 1^k=1 (mod 9) for any integer k>0. It follows that n is congruent to a_0+a_1+...+a_{m-1} (mod 9). Therefore, n is divisible by 9 if and only if the sum of its digits is divisible by 9.
Thanks for the censorship and banning a contributing member of the mathematical community from your forum. If you cannot take criticism, then get off the internet. For all who may view this video, do not post anything in the forum that goes against "Albert Einstein" (my ass) or else you'll be kicked out of his little club. My suggestion to you, "Al," is to suck it up and why not debate with someone who may have formal training in mathematics beyond high school. Maybe you'll be surprised.
@trustinthestars I'm sorry, all you did was come onto the forums and start explaining how what I am attempting to start is not new and that the forum would be un-succesful... I saw no need for the post so I removed it... It seemed that you were just trying to start a fight, that's why I banned you. Because your first and only post was bashing on the forum itself. It seemed you weren't actually interested in being a part of the community, just attempting to tear it down?
@orangegold1 Is that not a proof of the fact? You don't understand that if you can't prove it, it's not true?
musicmantribalx 6 months ago
That's like the same as EasyCal! (glad2teach . co . uk)... except the easycal tricks go way on to...well...huger(infinite digits times infinite digits) multiplications mentally, and they were passed from ancient india 3000 years ago... so ha!
randomwindowsstuffz 7 months ago
thanks for posting these videos man. do these work all the time with all numbers?
urumqilik 7 months ago
Pretty cool...the times 11 trick is well-known but I never quite applied until I saw it here.
The division by 9 trick I have never heard of but it is faster than long division for short numbers. I'm curious what is the proof of the division by 9 trick?
JamesMazur2 7 months ago
@JamesMazur2 There is no proof! That's why it's decimology.. It's simply numbers working together.. no algebraic reason why!
orangegold1 7 months ago
@orangegold1 Let n be an m digit number, whose digits are a_0, ..., a_{m-1}. First, note that 10 is congruent to 1 (mod 9). Hence, 10^k is congruent to 1^k=1 (mod 9) for any integer k>0. It follows that n is congruent to a_0+a_1+...+a_{m-1} (mod 9). Therefore, n is divisible by 9 if and only if the sum of its digits is divisible by 9.
musicmantribalx 6 months ago
PRETTY NEAT.
quest33613 7 months ago
Thanks for the censorship and banning a contributing member of the mathematical community from your forum. If you cannot take criticism, then get off the internet. For all who may view this video, do not post anything in the forum that goes against "Albert Einstein" (my ass) or else you'll be kicked out of his little club. My suggestion to you, "Al," is to suck it up and why not debate with someone who may have formal training in mathematics beyond high school. Maybe you'll be surprised.
trustinthestars 7 months ago
@trustinthestars I'm sorry, all you did was come onto the forums and start explaining how what I am attempting to start is not new and that the forum would be un-succesful... I saw no need for the post so I removed it... It seemed that you were just trying to start a fight, that's why I banned you. Because your first and only post was bashing on the forum itself. It seemed you weren't actually interested in being a part of the community, just attempting to tear it down?
orangegold1 7 months ago
@trustinthestars If you would like I will unban you... It just appeared that you didn't want to be a part of it.. Feel free to visit and post now.
orangegold1 7 months ago
@EuriaAgentWolf Thanks! I'm excited!
orangegold1 7 months ago
OH SHI~
awesome!
TamPonchik 7 months ago