Mathemagic Addition - Click the Green Flag to start Then follow the on-screen Instructions to learn how to prepare 4 Strips of Paper enabling you to perform the Mathemagic Addition Trick and trick someone. Click the [NEXT] button (or anywhere right of the Paper Strips) to see the next Instruction Slide. NOTE: Upgrade ... you can now Flip/Swap the Strips of Paper at any time during the "how-to" Slide Show. Also the randomly generated digits for each Number (both sides) have no repeats. Furthermore no randomly chosen digit in Slots 2 or 3 on any Strip is a repeat of any other digit in Slots 2 or 3 on that Strip. Additionally no digit in Slot 3 of a Strip is allowed to be (9 - one already chosen in Slot 2 of that Strip). None of the conditions/restrictions above (& used by this project) are necessary for the trick to work, they just help to disguise the mathematical trickery involved. Special thanks to @colinmacc for his clarity of thought in showing me how to effectively create my own: "create a clone of myself and wait" block. This also exposed an "issue" where the conditions above I want to impose on the choice of digits, are occasionally too restrictive and cannot be satisfied. It happens quite rarely (maybe once in every 1-100 Flag Clicks), so when it does, a Warning message pops up, and when you want, just Click the Message and it will Try Again!
Created by @gregatku for use in Maths Problem Solving Classes for Kids Unlimited. Inspired by a Zoom meeting I was called in to witness, with a Magician named Tim. Tim teaches Magic to young kids, and Kids Unlimited are looking into maybe engaging his services to help us to do likewise. I told him a simple Mathemagical trick I knew, and he decided to show us his Mathemagical trick. After telling him how to Swap & Flip his strips of Paper, I was impressed that he could tell us the sum of the 5 numbers formed in a flash! Naturally I got the calculator out on my phone and added up the 5 numbers to prove that he had indeed given us the correct Sum. He then told us that young kids love this trick and the fact that they can often even fool their Maths Teachers with it. He also told us that it was as easy for them to perform as "subtracting 2". When I got home later that day, armed with the addition sum still on my calculator & his "subtracting 2" hint in mind, I spent the next few hours working out how the trick worked and how the Paper Strips were pre-prepared. I'd been searching for a good idea for a new Scratch project. So a week later I thought that maybe I could make a project to teach kids how to do the trick. So here it is! Initially I had no idea how to build it and it just grew by osmosis and trial & error. It is a bit clunky and I am sure there are much better ways of coding it, but I think it serves its purpose well enough and I am quite happy with it. Once you have made your Paper Strips, to perform the trick, you get the person you are trying to impress, to Flip & Swap as many Strips as they wish. When they are done, you write down the answer which you can work out in a flash on a piece of paper that you fold to hide what you wrote, and you tell them "I have written down the answer!". This may well cause them to ask you "But what's the question?". Whether or not they do that, you need to tell them the question is "What is the sum of the 5 different 4-digit numbers shown across the Strips?" Then you tell them to add up the numbers (with or without a calculator), and when they have finished, you unfold your piece of paper with answer you wrote on it, show it to them, and ask "So, this is the total you got, right?" In one of the Slides, I suggest that "Once you understand how the trick works, you can prepare the Strips in sneakier ways to better disguise the trickery involved". These are as follows: 1). In this project the first three numbers are chosen randomly, in a specified way to simplify coding, but in reality if you follow the instructions as specified for setting the 1st number on each Strip and its flip-side, you don't need to follow the instructions exactly for determining where to put the 2nd and 3rd digits on each Strip. You do need to follow the instructions for choosing the Value, but that Value doesn't need to always go in the 2nd and 3rd slots on the Strip. The chosen Value can be placed in any 2 vacant slots on that Strip, ideally in different slots on each Strip. Then when setting the 4th and 5th digits in the remaining 2 vacant slots, then all you need to do is set each of the 2 remaining vacant slots on each side of each strip, to 9 less the value of one of the now-non-vacant slots (but not the one in 1st slot) so you end up with each side, having 2 pairs of values that add to 9, filling the last 4 slots. Preparing the Strips this way makes working out how the trick works, considerably more difficult to deduce than this Project's approach. 2). It is also helpful to have a 1 in the 1st number (& on the flip-side), because it increases the chance that one of them will be the last digit (but you can't be sure because the person you're tricking can swap/flip the Strips around however they wish). But if a 1 does end up on the right, subtracting 2 from it affects both the last 2 digits in the Sum, so it is more difficult for the person you're "tricking" to detect how you did it. 3). But perhaps the simplest disguise to how you do the trick, is not to put the 1st Number that you use to work out the Sum (by adding 20000 & subtracting 2 from it) in the 1st slot ... It could be placed in the any of the 2nd to 5th slots instead. But remember to calculate the Sum, from the number in that new slot (not the 1st slot). If you do this it's good to make sure the new Number in the 1st slot doesn't have a zero in it. I have now added a simple demonstration of the 3rd of those sneaky disguises above, to the Project. Hope you have fun making your own set of Mathemagic Addition Strips and then using them to trick somebody. PS: For anybody who actually goes to the trouble of making their own set of Mathemagic Addition Strips, I would love to know of any successes, especially if you managed to fool somebody important with it. If so, please tell me about it in the Comments! Regards Greg
