This one has me stumped.

[Ualaa]

http://www.regiftable.com/regiftingrobinpopup.html

[Zub]

the calculations always give a multiple of 9 (18, 27, 36 etc)
all those cells contain the same "gift"
so the answer is always correct, no matter what number you chose

[Ualaa]

Hmm.

Yeah, once you point that out, its pretty easy to spot.

[Zub]

to clarify: any 2 digit number can be split into (10x + y)
if you remove 1x and 1y you get a number that is equal to 9x, and therefore a multiple of 9

[Zub]

Hmm.

Yeah, once you point that out, its pretty easy to spot.
yeah it's one of those "Damn, but OF COURSE!" moments :-)

[remanz]

nice trick. Got me for a sec there. Then i saw the board is randomly generating gifts. 9x shows up. I thought I was going mad. the board is fixed. and it picks right everytime.