Company: Landeed IIT Kharagpur
Difficulty: medium
Probability of Divisibility by 12 Problem Description In an intricate game of chance and numerical strategy, participants are tasked with repeatedly rolling a specially designed 11-sided die. This die is perfectly fair, meaning each of its faces, uniquely numbered from 1 to 11, has an equal chance of landing face up. The central objective of this particular game phase is to continue rolling the die until the ongoing product of all the numbers rolled sequentially achieves divisibility by 12. This creates an escalating numerical challenge for the player. Given these precise rules governing the game mechanics, this scenario poses a fundamental question: what is the exact probability that the cumulative product will become divisible by 12 for the very first time on the third roll, and not on any preceding roll? Runners on a Circular Track Problem Description A common scenario in athletic training involves two runners, designated as Runner A and Runner B, navigating a perfectly circular tra