MathDB
2013 preRMO p5, balls, n-1 red, n green, n+1 blue

Source:

August 8, 2019
combinatorics

Problem Statement

There are nāˆ’1n -1 red balls, nn green balls and n+1n + 1 blue balls in a bag. The number of ways of choosing two balls from the bag that have different colours is 299299. What is the value of nn?
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