Recreational Math- Mathemagics

J. SriskandarajahAMATYC Conference

Las Vegas, November 13, 2009

1776 and Abraham Lincoln (02-12-1809)

• 1776 is not only a significant year, it’s a fascinating number!

• Think of a positive single digit

What’s fascinating about 1089?• Write any non symmetric three digit

number• Reverse your original number• Express the positive difference as a

three digit number• Now reverse this difference• Then add the above two numbers• The answer is…….

Learn more about 1089

• It’s a perfect square, 33^2

• It’s the only four digit number when multiplied by 9 will produce its original number in reversed order: 9801 which is another perfect square, 99^2

Become a psychic in 2009Age by dining out?

• Pick the number of times a week you would like to dine out (0-7)

• Times this number by 2• Add 5 to this number• Multiply this by 50• If you have already had your birthday

this year add 1759, else add 1758• Subtract the four digit year you were

born

Chocolate Math

• The above activity could be rephrased as seen in the following link:

• H:www.matcmadison.edu\jsriskandara\My documents\Chocolate Math

• Note, 2009 is NOT prime but 7X7X41

Mathemagics and Recreational Mathematics continued…..• Mind Reading• Super Computation• Spelling and the Math connection• Predicting a three digit number,

house number, card etc.,

Is 2009 special?

Number a 7X7 square, 1-491 2 3 4 5 6 78 9 10 11 12 13 1415 16 17 18 19 20 2122 23 24 25 26 27 2829 30 31 32 33 34 3536 37 38 39 40 41 4243 44 45 46 47 48 49

Interchange rows randomly

• 15 16 17 18 19 20 21• 36 37 38 39 40 41 42• 1 2 3 4 5 6 7• 22 23 24 25 26 27 28• 43 44 45 46 47 48 49• 8 9 10 11 12 13 14• 29 30 31 32 33 34 35

Now interchange columns randomly

• 17 21 15 20 18 16 19• 38 42 36 41 39 37 40• 3 7 1 6 4 2 5• 24 28 22 27 25 23 26• 45 49 43 48 46 44 47• 10 14 8 13 11 9 12• 31 35 29 34 32 30 33

Add 262 to every entry

• 279 283 277 282 280 278 281• 300 304 298 303 301 299 302• 265 269 263 268 266 264 267• 286 290 284 289 287 285 288• 307 311 305 310 308 306 309• 272 276 270 275 273 271 274• 293 297 291 296 294 292 295

Add the seven numbers on either diagonal, aha!

• 279+304+263+289+308+271+295 = 2009!

• 281+299+266+289+305+276+293 = 2009!

For an even more amazing result,

• Highlight any entry on the table and cross out all the other entries in the same row and column. Continue this process with the remaining entries until you have just seven entries all on different rows and columns.

Amazing sum of 2009!

283301

263288

310272

292

272+283+263+310+301+292+283 =2009!!