by jlucero Sat Dec 07, 2013 4:55 pm
First, recognize that you need to solve for project manager (PM), team leader (TL), and consultants (C) separately:
PM: one slot, two people = 2
TL: one slot, three people = 3
C: four slots, seven people = 7 * 6 * 5 * 4. With the slot method, you need to then stop and realize that there are 4! ways to rearrange the four people you have chosen. So you need to divide 840 by 24 to get 35 unique teams that can be created. Finally, since 2 of the consultants can't work together, we need to remove these specific teams from the 35 possibilities. If these two people are selected, we have two slots remaining with five other people to fill those slots, so there are 5 * 4 = 20, different ways to select the two other people, divided by 2, because there are 2! ways to choose those two other people. This means there are 35 - 10 = 25 consultant teams that can be selected.
Overall: 2 * 3 * 25 = 150
Joe Lucero
Manhattan GMAT Instructor