"Ape alone... weak. Apes together... strong."
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Caesar
The Apes are gathering resources for the upcoming winter. This time, Caesar and others went gathering wood. To store the gatherings, Maurice - a wise ape, and Caesar's best friend - has devised a plan on how the resources should be distributed:
All the logs are to be divided into n piles. After this, n 1 -th of the logs from the first pile are to be shifted into the second pile. Then, n 1 th of the logs in the second pile, after the first transfer, are to be shifted into the third pile. Next, n 1 th of the logs in the third pile, after the transfer from the second pile, are to be shifted to the fourth, etc...
Finally, from the n -th pile, n 1 th of the logs in the n -th pile, after the previous transfer, are to be shifted to the first pile. After that, each pile will have A -amount of logs.
Caesar and Maurice agreed to divide the resources into 1 0 1 piles.
If, before shifting, the amount of logs in piles 1, 2, and 3 combined is 1 5 0 , how many logs were gathered?
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these apes are too legit
@John Muradeli : Requesting a solution, or at least the number of logs initially in the piles.
I think there is issue with the problem statement.
The problem states that:
Finally, from the n -th pile, n 1 th part of the logs that were moved there in that last transfer are shifted to the first pile.
This means nothing was moved out from the original logs in n t h pile. The movement happened only from the logs that were moved to the n t h pile from the ( n − 1 ) t h pile.
However, looking at your solution, it seems that the n t h pile case is no different than ( n − 1 ) t h pile case.
Hence, it should have been mentioned like this:
Finally, from the n -th pile, n 1 th of the logs, after transfer from the ( n − 1 ) t h pile, are shifted to the first pile.
"Caesar and Maurice agreed to divide the resources into 101 piles" All piles have the same amount of logs.
"If, before shifting, the amount of logs in plies 1, 2, and 3 combined is 150..." Piles 1, 2, and 3 have a combined number of 150 logs.
Each pile has 3 1 5 0 = 5 0 , so 101 piles would be 5 0 ∗ 1 0 1 = 5 0 5 0
Ah - clever smarty-pants, eh?
You found quite the loophole in my problem.
(And I hope you did manage to solve it the way it was supposed to be solved as well).
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Simpler is better? Anyway, I'll try it the other way too. Thanks.
Note that it is not stated that "all piles have the same amount of logs" at the start.
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Let the first pile initially have x 1 logs, the second pile x 2 , etc.; the last ( n th) pile will thus have x n .
The first pile is in a special position because n 1 logs are initially withdrawn from it, and at the end of the process is it replenished in from the n th pile, whereas all other piles are first filled with logs from the previous piles, and only then have n 1 th of the logs withdrawn from them.
So, let us observe any pile but the first pile. Let's call our pile k . Initially, it had x k amount of logs, and a certain amount of logs were added to it - let's call it y - from the ( k − 1 ) th pile. Then, from the overall sum of logs of y + x k logs was withdrawn a n 1 th part. So we're left with ( y + x k ) n n − 1 logs (in that pile). Thus,
( y + x k ) n n − 1 = A . → ( 1 )
In the previous - ( k − 1 ) th pile, if it wasn't the first pile (i.e. if k = 2 ), it must've had A logs. (The first pile only acquires A amount of logs after it is replenished from the n th pile). Therefore, before the transfer of y logs it held A + y logs. By the condition the withdrawn amount of y logs constitutes n 1 th part of A + y , i.e.
y = n 1 ( A + y ) . → ( 2 )
From here we find y = n − 1 1 A . Substituting this into the first expression, we obtain x k = A .
Hence, in every pile (maybe with an exception of first and second piles - prior to being excluded from consideration), there were initially A logs:
x 3 = x 4 = . . . = x n = A . → ( 3 )
The unknown x 1 can be found in a following way; by the condition, x 1 has n 1 th of its logs withdrawn from it. We're left with x 1 n n − 1 logs. At the end of the process, a certain amount of logs - y - is added to it from the last pile. Hence,
y + x 1 n n − 1 = A . → ( 4 )
Applying the same reasoning to the n th pile, we find that y = n − 1 1 A . Inserting this into expression ( 4 ) we obtain
x 1 = ( n − 1 ) 2 ( n − 2 ) n A . → ( 5 )
To investigate for x 2 we dig up
( n 1 x 1 + x 2 ) n n − 1 = A , → ( 6 )
where x 1 is determined by expression ( 5 ) . Solving this equation, we obtain
x 2 = ( n − 1 ) 2 n ( n − 1 ) − ( n − 2 ) A .
And thus,
x 1 = ( n − 1 ) 2 n 2 − 2 n A ; x 2 = ( n − 1 ) 2 n 2 − 2 n + 2 A ; x 3 = x 4 = . . . = x n = A .