Question: Committee of 4 people

Comment on Committee of 4 people

why cant we calculate it like: 8*7*6*5?
gmat-admin's picture

You are breaking the task into 4 stages (select 1st student, select 2nd student, select 3rd student and select 4th student).

HOWEVER, when you do this, you should ask "Does the outcome of each stage differ from the outcomes of the other stages?" (for more on this, watch: https://www.gmatprepnow.com/module/gmat-counting/video/788)

In this case the answer is no; each selected person gets to be on the committee. That is, selecting A then D then E then B, is the SAME as selecting E then B then A then D

As such, we cannot use the stages approach. Instead, we must use combinations.

Hi Brent!!
can you help me please on this one ?
in how many ways can 12 different books be distributed equally among 4 different boxes?
i will really appreciate it!!
thanks
gmat-admin's picture

Here's my full solution: https://gmatclub.com/forum/gmatbuster-s-weekly-quant-quiz-10-ques-282406...

For some reason, the 5 posts above mine all have the same wrong solution. As you can see from my solution, we can distinguish the 4 boxes by naming them box #1, box #2, box #3, and box #4. So, there's no need to multiply our answer by 4! at the end (as all of the 5 other posts have done)

Cheers,
Brent

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