More Mathemagic Click the Green Flag and follow the Instructions. This is a neat bit of mathemagic that simplifies the process of multiplying 2 large 2-digit numbers. For the record input numbers are restricted to those > 87, for 2 reasons: 1) it ensures the one actual multiplication done is one that most people can also do in their head, and 2) it significantly reduces the possibility of that multiplication being a 3-digit result, which if it was, would require the leading digit to be carried over to the first 2 digits of the end result (that have already been set) thus causing those pre-set first 2 digits to be increased, in which case the trick doesn't look quite as neat!
Created by @gregatku specifically for the Scratch Design Studio - Magic Tricks (until I remembered one is only allowed to have one project in an SDS, so I didn't request that it be added to that Studio). if you like this bit of Mathemagic you might also like my Easy Mathemagic Trick project - https://scratch.mit.edu/projects/847735140/ and my Mathemagic Addition project - https://scratch.mit.edu/projects/706308013/ For those interested this is why the trick works. This is the actual calculation the project performed on the 2 numbers X and Y: 100 * (X - (100 - Y)) + (100 - X) * (100 - Y) = 100X - 10000 + 100Y + 100 * (100 - Y) - X * (100 - Y) = 100 * (X + Y) - 10000 + 10000 - 100Y - 100X + X * Y = 100 * (X + Y) - 100 * (X + Y) + X * Y = X * Y That is: 100 * (X - (100 - Y)) + (100 - X) * (100 - Y) = X * Y So the trick actually works for any 2 numbers X and Y, not just those > 87! Trouble is for small numbers the trick would actually be more complicated than traditional multiplication.
