SOLUTION: If there are 30 students in the class and we need to select a President and Treasurer for our meetings, how many possibilities are there?
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Question 1136511: If there are 30 students in the class and we need to select a President and Treasurer for our meetings, how many possibilities are there? Found 2 solutions by rothauserc, ikleyn:Answer by rothauserc(4718) (Show Source):
You can put this solution on YOUR website! The problem asks for the number of combinations of 30 students taken 2 at a time
:
30! / (2! * (30-2)!) = (30 * 29) / 2 = 435 combinations
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Note combination means that order of selection is not important
:
In this problem, the order of persons at given positions is IMPORTANT:
John as the President and Alice as the Treasurer is not the same as Alice as the President and John as the Treasurer.
Therefore, the answer in this problem is 30*29 = 870.
There are 30 choices to select a President from a pool of 30 students, and 29 choices to select a Treasurer among remaining 29 students.
This problem is NOT ABOUT COMBINATIONS - IT IS ABOUT PERMUTATIONS.
It is always so, when the problem says about selections to distinguishable named positions.
