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usre123
Joined: 30 Mar 2013
Last visit: 25 Nov 2022
Posts: 74
Own Kudos:
Given Kudos: 197
Location: United States
Schools: Alberta '23 (WL)
GMAT 1: 760 Q50 V44
23 Sep 2014, 08:42
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amkabdul
Agreed about the permutations approach. I was under the impression that we use permutations when there are places specified in the group, as there are here. I dont understand the combinations approach at all. For eg, in how many ways can you select a president and VP from a group of 6. Should be 6*5=30, or 6P2= 30.
Can someone please point me in the direction where I can understand when to apply C and when to apply P. I understand that P is applied when order is imp, but the problem is, that when selecting president and VP from a group, order shouldn't be important. AB or BA is the same, and therefore, even those should be solved by using combinations. I hope I'm explaining my confusion well enough for someone to help me
23 Sep 2014, 10:38
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usre123
If you're choosing a President and Vice-President, and you choose A for President and B for VP, that's very different from choosing B for President and A for VP -- you have a different President! So when you're choosing a President and VP, order is very important, and AB and BA are not the same selection.
25 Jan 2017, 11:22
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rvthryet
We are given that there are 10 boys available to fill the following positions:
1 goalkeeper, 2 defenders, 2 midfielders, and 1 forward.
We are also given that only 2 of the boys can play goalkeeper.
Thus, we can select the goalkeeper in 2C1 = 2 ways.
We now have 8 boys left and need to select 2 defenders from those 8 boys:
8C2 = (8 x 7)/2! = 28 ways
We now have 6 boys left and need to select 2 midfielders:
6C2 = (6 x 5)/2! = 15 ways
We now have 4 boys left and need to select 1 forward:
4C1 = 4
Thus, the number of ways to select 6 starters is:
2 x 28 x 15 x 4 = 3,360
Answer: D
