5614 Posted January 14, 2005 Share Posted January 14, 2005 Make the number 21 using the numbers: 1, 5, 6, 7 you can use: addition, subtraction, multipliaction and division I promise you it is straight forward maths and NO tricks... you can only use each number once and you cant use say 15 (the 1 and the 5 together) and you cant do like 5^6 or anything. Link to comment Share on other sites More sharing options...
YT2095 Posted January 14, 2005 Share Posted January 14, 2005 according to my calculations it is NOT Possible. unless you allow the addition of 1 and 0 in a ten or a 2 an 0 in a twenty to make a 1 or a 2 for example. other than that, I don`t think it`s possible. Link to comment Share on other sites More sharing options...
MolecularMan14 Posted January 14, 2005 Share Posted January 14, 2005 6/(1-(5/7)) Link to comment Share on other sites More sharing options...
YT2095 Posted January 14, 2005 Share Posted January 14, 2005 wow! it beats my: 7x1= 7 5x6 = 30 3+0 =3 3x7 =21 anyday ) Link to comment Share on other sites More sharing options...
MolecularMan14 Posted January 14, 2005 Share Posted January 14, 2005 lol, i do what I can Link to comment Share on other sites More sharing options...
5614 Posted January 15, 2005 Author Share Posted January 15, 2005 have you heard it before or had any help with it? it took me a while to guess, i knew it must be divide by a number smaller than 1 but my calculator i was using was giving me stupid decimals which got confusing! Link to comment Share on other sites More sharing options...
5614 Posted January 22, 2005 Author Share Posted January 22, 2005 anyone in the UK and belongs to Mensa? if my dad remembers he said he'd send it into the magazine. Link to comment Share on other sites More sharing options...
MolecularMan14 Posted January 22, 2005 Share Posted January 22, 2005 Actually I knew that (after trying all my multiplications) if I was dividing something by 6, it would have to be less than one, so I tried subtracting one what I knew to be a decimal, giving me something like .2857~ect... I checked it over, and it worked Lucky guess really Link to comment Share on other sites More sharing options...
Guest maxscud Posted May 22, 2005 Share Posted May 22, 2005 hmm... (5*6) - (7*1) = 21 lols Link to comment Share on other sites More sharing options...
Skye Posted May 22, 2005 Share Posted May 22, 2005 That equals 23? Link to comment Share on other sites More sharing options...
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