Exam PMP Topic 1 Question 1729 Discussion

5*4/2 = 10, If you are the PM and have four stakeholders to communicate with, there are 5 people involved and 10 channels. When you add a new stakeholder, you have 6 people and 15 channels. The formula stated in this question is N(N-1)/2 where N equals the number of people. How to derive this Formula: The Attached calculation will help to realize the concept of communication channel. Say, there are "n" Persons and they are having communication with each other. We need to find how many communication channels are possible here. Take the case of the first person. He can communicate with rest of the (n-1) person. So, here are (n-1) communication channels. The Second person can communicate with ((n-1)-1) person because his communication with the first person is already taken into account for the calculation of first person. So, here are (n-2) communication channels. Similarly, the third person can communicate with ((n-1)-2) because his communication with the first and second person is already taken into account for the calculation of first and second person. So, it's (n-3) channels.Like that, if we proceed, the total no of Channels used by n person, will be = (n-1)+(n-2)+(n-3)+......+1 = 1+2+3+.....+(n-1)We have a sum of an AP series for "(n-1)" number whose first number is "1" and the common difference is also "1".The Formula for Sum of AP series is: S = n[2a+(n-1)d]/2(where, n = total numbers, a = first number, d = common difference) So, it gives us the Total Communication Channel=(n-1) *[2*1+((n-1)-1)*1]/2 = (n1)*[2+(n-2)]/2 = n*(n-1)/2 Hope this helps.