For all you mathemaicians out there. Step by step using your finger add the following in your head. If you get the answer of 5,000 try again. If you get 5,000 again you'd better give up the mental gymnastics and use a calculator. Please Register or Log in to view the hidden image! Take 1000. Add 40. Add another 1000. Add 30. Add 1000 again. Plus 20. Plus 1000. And plus 10. What is the total ?
Interesting phenomena. Mentally you get 5,000. By calculator (and taking a macroscopic view) you will see it is 4,100.
Rappaccinni, Please Register or Log in to view the hidden image! Was that mentally or with a calculator?
Why would anyone get 5,000? I mean, I suppose if one weren't really paying attention, but you gave it away too soon, so one would already be alert for a mental slip-up of some kind, and thus careful to keep place-values in order.
It's all in the noggin, baby. Please Register or Log in to view the hidden image! Edit: Oh... I just realized what the challenge was. Haha! Uber-cool! ... Maybe I'll try not to be jackass one day. One day. Tomorrow, Tomorrow. It's only a daaaaay aaaaaahhhh wayyyyyy! Please Register or Log in to view the hidden image!
Errandir, Let me suggest, you now know the answer, still take your finger and step by step go down and add up the column. Get back to me when you have done it. Please Register or Log in to view the hidden image! Take 1000. Add 40.......................=1,040, yes? Add another 1000........=2,040, yes? Add 30.......................=2,070, yes? Add 1000 again...........=3,070, Yes? Plus 20.......................=3,090, yes? Plus 1000....................=4,090, yes? And plus 10.................=5,000, yes? But: 1,000 1,000 1,000 1,000 ....40 ....30 ....20 ....10 ------------ = 4,100!!, yes?
Can I cheat and add 1000 3 times and then add 40 + 30 + 20 + 10? That's always the way I add things in my head - simplify
Did anybody fall for this? It doesn't look like it. Please Register or Log in to view the hidden image!
I fell for it, it's quite natural. There's a certain step in the counting that induces some kind of malfunctioning. If you add the numbers as pbm suggested, the step will be avoided.
I've encountered this supposed trick before. I didn't fall for it, even though I followed the method of calculation given, rather than PMB's method. Supposedly, a lot of people do fall for it, though. It must be something to do with that last step, adding 10 to 4090 and getting 5000, instead of 4100.
I added the 100s and the 1000s seperately, and didn't have a problem. Then I wnt back 'knowing' the answer, and got 5000. Interesting.
Persol, Glad I wasn't the only one. Please Register or Log in to view the hidden image! I wonder if it isn't the power of suggestion. That is left to add the column without suggesting 5,000 as an answer one would likely not make the mistake.
How does one do a sum "in your head" while "using your finger"? Stick your finger in your ear? Anyway, why do you assume people will do it wrong? Yes, of course the sum is 4100. That's what most people will get, isn't it? Or are you telling us that YOU couldn't do it in your head?
HallsofIvy, Actually there seems to be an inordinate number of people that do get it wrong. Even Persol admitted that he did it wrong after knowing the correct answer. Even that is not completely unique. I have had others say the same thing from other sites where this is posted. The fact that you may not make the error is simply a matter of mind set. An ingrained process that you don't deviate from in doing mathematics. This is somewhat like optical illusions where you look at something once and then again see something entirely different another time. Curious, how receptive do you think you are to optical illusions?
Holy mother of pearls I got 4,100 adding it in my head. I almost slipped up at the end and can see why 5,000 would be achieved as an answer but I actually dodged a bullet. Go me.
