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You and your two friends Pip and Blossom are captured by an evil gang of logicians. In order to gain your freedom, the gang’s chief, Kurt, sets you this fearsome challenge.
The three of you are put in adjacent cells. In each cell is a quantity of apples. Each of you can count the number of apples in your own cell, but not in anyone else’s. You are told that each cell has at least one apple, and at most nine apples, and no two cells have the same number of apples.
The rules of the challenge are as follows:
The three of you will ask Kurt a single question each, which he will answer truthfully ‘Yes’ or ‘No’. Every one hears the questions and the answers. He will free you only if one of you tells him the total number of apples in all the cells.
Pip: Is the total an even number?
Kurt: No.
Blossom: Is the total a prime number?
Kurt: No
You have five apples in your cell. What question will you ask?
THIS should be the question that you need to ask!
What was the challenge?
Remember, all you have to do is that ask one crucial question to logicians and not necessarily deduce the total count of apples.
Since, each cell has 1 to 9 apples and no two cells have same number of apples, the lowest count of apple is 1 + 2 + 3 = 6 and the highest count would be 7 + 8 + 9 = 24.
That is the total number of apples could be between 6 to 24.
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Now, Pip and Blossom already have gathered some information about the total.
1. The total is not an even number - Hence, only numbers 7,9,11,13,14,15,17,19,21,23 can represent the total count.
2. The Total is not a prime number - Out of the number above, only 9, 15, 21 are non-prime number.
Hence, the total count must be among 9,15 or 21.
Now, your task is easier. All you need to ask the Kert below question -
"Is total is 15?"
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CASE 1 : Total is really 15 -
Then Kert would reply with YES to your question and all of you know the total now.
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CASE 2 : Total is 9 -
The Kert's answer to your question would be NO.
If the total is 9 and you have 5 apples then rest of 4 apples must be distributed among Pip and blossom as (1,3) or (3,1) but can't be (2,2) since no 2 cells can have same number of apples.
Now, the friend having 1 apple (or 3 apples) can think that the total can't be 21 as in that case other 2 must have total of 20 (or 18) apples. But the maximum that other two can have is 9 + 8 = 17 apples.
So any of them can deduce that the total is 9.
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CASE 3 : Total is 21 -
Since you have 5 apple other 2 must be having total of 16 apples. One of them must be having 7 apples and other having 9 apples.
The friend having 9 apples can easily deduce the count as 21 since 9 as a total count is impossible in the case as for that the other must have 0 apples.
And the friend with 7 apples know that other can't have 1 + 1 or 2 + 0 (as per given data) apples in order to have total count of 9. Hence, he too can deduce that the total must be 21.
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To conclude, depending on the what Kert answers to your question and the count of apples that each of other 2 friends have one of them (or you too if count is 15) can deduce the total number of apples easily. And eventually, logicians have to set you free as promised.
