2013 AMC 12A Problem 17
Problem 17 of 25IntermediateNumber TheoryCounting & Probability
A group of pirates agree to divide a treasure chest of gold coins among themselves as follows. The th pirate to take a share takes of the coins that remain in the chest. The number of coins initially in the chest is the smallest number for which this arrangement will allow each pirate to receive a positive whole number of coins. How many coins does the th pirate receive?
Answer choices
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Solution
For the number of coins before the th pirate takes a share is times the number afterward. So if coins are left for the th pirate, the initial count is
The smallest making this a positive integer is Before pirate the remaining count is the initial count multiplied by substituting this shows it is an integer for every Hence all shares are integral, and the th pirate receives coins.
Thus, the correct answer is D.