My friend had once done this to me and my jaw dropped straight down when he showed me the number, then i asked him how he did it and then he said nope not telling you! so then i saw this video and now i under stand how he did it! Thanks! : )
Great video, this is a very clever and unexpected math trick. Your videos are fantastic. I will be looking back on some of your earlier work on factoring for an upcoming exam. You've taught many people a lot of math. Thanks
If you saw this without watching to the end of the video, then you are very observant (and I congratulate you). I have done this trick about 25 times in front of classes, and I have never had anyone observe that without being told. Well done.
Yes it does. Every time I try it with a new class, and as a substitute teacher, I try this over 20 classes a year. I was also a regular full time teacher for over 37 years, and I tried it with these classes as well. They were all impressed, right up to grade 12 Math. I am sorry that it did not impress you (as you are obviously at a much higher level in thought as these mere mortals), but I will continue to use it with new classes I bump into.
@Haelstrome : Yes, I have shown it to Grade 12 classes and my very good Advanced Placement Calculus class. You couldn't have figured out what I did after I had written the first number, because you didn't know what I was going to do. I think that you are being to critical, maybe it is the way you deliver the "magic" that makes it cool. Try it on a few people, see what happens. Just make sure no digits are repeated or in an obvious patter. Have fun, you're allowed to!
you got it. well, x / 2 and then whatever steps I decide to add after it. The point being that the final answer has nothing to do with the original number chosen by the spectator
Messed around with this, and I noticed that if you attempt this with the number 8 instead 9, you end up with an initial subtraction of 224 instead of just 2 (If you do this with 3 digits). But you still add the two in the beginning. The only problem with this way is that if your target puts a 9, you would have to do the math in order to make sure that the calculations are right, and often you will be using less digits than what you started with.
If one of the numbers that the other person gives me starts with a 1, what number would I choose? Keeping in mind the numbers have to be under eight thousand? Thanks!
Yes, I added my own numbers, but in real time, each number I added within abut 10 seconds. If I knew the answer and was doing all the work in my head, I would be a genius at mental math. I have done this trick in front of classes of up to 30 students from grades 9 to 12 over 20 years, and NOT ONCE have they failed to be amazed, because I put my numbers down so fast that I could not possibly be doing it in my head. Watch to the end of the video to see how I get my answers so quickly.
Yes, you need the -2. Simply adding 20000 will be incorrect because you aren't adding 2*10000, you are adding 2*9999, which equals 19998, which is 20000-2.
The guy who made this videos grandaughter : hi, I was in the audience when my grandpa did this trick, and it was not fake. I'm 14, and quite enjoy math, and my grampa happens to be a high school math teacher and is very smart! so watch what you say! :)
Again, I am a Math teacher. The trick works through algebra, not any "fake audience". The three people who helped me out here had never seen the trick before. They were 11, 13 and 57 and were all quite surprised, so the sound track is real.
You're right, a fifth grader can do this trick AND wow his parents and classmates. I have shown this trick to hundreds of classes from grade 8 to grade 12, and they all are impressed. None have got the "trick" until it is explained to them. Try it. Now, if you make sure there are no repeating numbers and no pattern to the 4 digits, it is harder to pick out the solution.
This is great!!! I did it to my family worked perfect :) one question what if the first number had a 1 at the end how do you subtract 2 ? Lets say the first number they give me is 3741 i would write on the other paper 2374_?????
Actually the numbers can be anything under 10,000. However, if they choose a number such as 9,538 I would have to reply with 0,461 in order for the two to have a sum of 9,999. This seems a bit weird for a four digit number to start with a "0", so I try to get people to choose numbers less than 9,000 so this does not come up.
if someone doesnt like or isnt impressed by another one's trick, presented sincerely, it's better he just keeps silent. learn to behave and respect orthers' effort to share. be a better person.
Don't be ridiculous, of course I cannot say "every" student was impressed. I did say that all the classes were impressed. Each class' reaction was one of disbelief, followed by "how'd you do that!". I then showed them the trick, explained how to tell others, and told them to pass it on. I'm sorry that I did not impress you, but then it's hard to impress someone so critical. Have a lovely life....
What part of the explanation did you not like. I am not going to tell students to "just subtract 2 to the first (one's) digit and make 2 your last digit (attach 2 to the front)" WITHOUT explaining "why" you do this. Thus, the explanation of 9999 is actually 10,000 -1 etc. Every trick that I explain, I also show the students "why" it works.
I know I shouldn't have made fun of the person's spelling, but I couldn't resist. Now maybe we could figure out that if a coculator did exist, what would it look like? Maybe a calculator shaped chocolate bar?
Most people (including myself), could not figure out the result that way, in their head, that quickly. Watch to the end of the video to see how I do it.
