On my 80th birthday my guests were presented with several sets of 4-digit numbers and challenged to create the number 80 using some (or all) of the 4 digits, basic math. signs (+,-,*,/,^ ,concatenation and brackets).
Examples:
n=1268; answers 16+8^2 or 68+12
n=3024; answers 320/4 or 20*4 or 40*2

More (for you to solve):
0269
0246
0468
0579
0126
1234
1469
1579
1645
2359
5555
8249
9999

(In reply to re: computer solutions for all but 2359 by Ady TZIDON)

Using the given ASCII symbols and applying the standard text notation for tetration, (2^^3)*5 will equal the requisite value of 80 -- the 9 being unused.  If required to be used, (2^^(9/3))*5 will also give the result.

Tetration, like exponentiation, is not considered basic math, i.e., an elementary function. Given the allowance of the symbol for exponentiation, an assumption has been made that the iterated functions of hyperoperations are permitted, with exponetiation being the most simple of the hyperoperations. For the comparatively miniscule value of 80 most hyperoperations will be useless in the creation of its representation, but not all as demonstrated above.

Edited on December 25, 2015, 8:11 am

Posted by Dej Mar on 2015-12-20 00:33:57