Puzzle 79 -Shopping

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Puzzle 15 : All but two

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Solution to puzzle 14 Huh, sending more money would have been much easier than this puzzle.      SEND     MORE   MONEY We have to find values for S,E,N,D,M,O,R,Y (8 digits out of 10).  Now, we're adding two 4-digits numbers.  Since 9999+9999 < 20000, M cannot be >=2. And by the "usual rules" for this kind of question, it can't be 0. So M=1 . Now, looking at the fourth (left-most) column, we have either S+1>=10 (if there's no carry) or 1+S+1>=10 (if there's carry). So S=8 or 9 , and O=0 or 1 . Since 1 is already taken, O=0   In the third column, we can't have E+0=N (no carry), so E+1=N and there's carry from the second column.   So in the second column either N+R=10+E=9+N, and R=9, or there's carry and 1+N+R=10+E=9+N, and R=8. So R=8 or 9 , just like S. IF S=8 and R=9,we're looking at 8END + 109E ====== 10NEY But this cannot possibly work: we need to get either E+0=10+N or 1+E+0=10+N i...
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Puzzle 128 - Kings and Queens

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 On a table, 3 normal playing cards are placed face down.  To the right of a king, there is a queen or queens. To the left of a queen there is a queen or queens.  To the left of a heart, there is a spade or spades.  To the right of a spade, there is a spade or spades.  Which three cards are on the table? (Borrowed from the book "The colossal book of short puzzles and problems" by Martin Gardner)  Show answer The first rule says that there is atleast one king. Second rule says that there are two queens. (KQQ,QKQ) Third rule says that there is a heart and a spade. And the fourth rule says that there are two spades. (HSS,SHS,SSH) Which means out of three cards, two are queens and one is king. And two are spades and one is hearts. So the four possibilities are   KS, QS, QH KS, QH, QS QS, KS, QH QS, KH, QS The fourth is an impossible option as there can't be two queen of spades in a deck. So the three possible answers are  King of s...
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Puzzle 119 - Prisoners with hats

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10 prisoners share a cell. The prison warden tells them that the next day they’ll be randomly lined up for execution. He’ll place either a black or white cap on everyone’s head. Each prisoner starting from the back of the line will guess what color his hat is. If he gets it wrong he’ll be executed.  Every prisoner can not see the hat on his head or of those behind him. He can see the hats of everyone in front of him.   How can the prisoners devise a strategy to save their lives?    You can find the solution here . 
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