JEE MATHEMATICS MCQ: PERMUTATIONS

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On a New Year day every student of a class sends a card to every other student. The postman delivers 600 cards. The number of students in the class is

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Correct option: C

Option C (25) is correct because it solves the permutation equation

{ }^n P_2=600

to find the number of students, n, where each student sends a card to every other student.

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