UPSC Prelims 2015·CSAT·Quantitative Aptitude·Combinatorics and Probability

Twelve people form a club. By picking lots, one of them will host a dinner for all once in a month. The number of dinners a particular member has to host in one year is

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Last updated 23 May 2026, 3:31 pm IST
  1. AOne
  2. BZero
  3. CThree
  4. DCannot be predictedCorrect

Explanation

The selection of a host each month is done "by picking lots," which means randomly. This process is repeated for 12 months in a year. Let's analyze the options: A) One: While the *expected* number of times a particular member hosts is 1 (12 months * 1/12 probability per month), this is an average over many years or many members. In any single year, due to random chance, a particular member might host more than once, exactly once, or not at all. B) Zero: This is a possible outcome for a member (they might not be picked at all), but it's not the guaranteed number for every member. C) Three: This is also a possible outcome, but not a guaranteed or fixed number. D) Cannot be predicted: Since the selection is random each month, the exact number of times a specific member hosts over the course of a year is subject to chance. It's a variable outcome that could range from 0 to 12. We cannot determine a fixed, definite number beforehand. Therefore, because the host is chosen randomly each month, the number of dinners a particular member has to host in one year cannot be predicted with certainty.
Quantitative Aptitude: Twelve people form a club. By picking lots, one of them will host a dinner for all once in a month. The number of dinner
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