This puzzle is from "The Moscow Puzzles" by Boris Kodemsky is from another era - when there were things like clocks which need to be wound each day. If not they would stop. The puzzle goes like this.
I have a wall clock which is the only source for knowing the time in my house. One day I forgot to wind the clock and it stopped. Luckily, I have a friend whose clock shows the correct time always.
I walk down to his house, see the time in his clock, stay for a while and come back. Now I know the time and adjust my clock. It is is showing the correct time again.
How did I do that?
Answer: I wind up the clock before leaving the house and set it at 12 o'clock. It starts running. When I go to my friend's house I notice the time. And just before leaving the house, I also see the time.
When I come back, I see the time on my clock.
That will show the total time elapsed since I left home.
Now since I know the time in my friend's house as soon as I enter his house and just before I left his house, I know exactly how much time I spent there.
I subtract this time from the time elapsed. I get the total time walking to and from friend's house.
I divide it by 2. I get the time required to walk down from his house.
Now I can set the time on my clock as the time on my friend's clock while I was leaving his home plus the time I used to walk from his house.
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...
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...
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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