# Chapter 3 - Probability - Exercises 3.112 - 3.137 - Applying the Concepts - Basic - Page 162: 3.122a

Pairs consist of two electrodes each. using partition rule: N = 6, n_{1} = 2, n_{2} = 2, n_{3} = 2 = 6! / 2! 2! 2! = 90