Guide #5 Word Problems Chp 6 Combinatorics

[femanan]

Hi, I am in need of help telling the difference in using anagrams (or combinations) vs. FCP (permutations). Specifically around page 116 and 117 with the two different examples.

I do not understand the difference between the two problems (pg 116 7 people board an airport shuttle vs. pg 117 3 of 7 standby passengers).

They both sound very similar to me. How are you able to differentiate between using the two methods? For problem pg 116 I could have easily done 7C3 7*6*5/3*2*1 to get 35 which is the answer for pg 117 and vice versa to solve problem pg116 via method from pg117 problem.

Is it because one explicitly asks for combinations on page 117? Whereas the other is asking for arrangements? I noticed reading closer that the crucial difference is that the people are not distinguishable whereas on the problem the seats are distinguishable...how can we tell for other problems that is the case? I can very well say I'm not going to distinguish between seats A, B, and C because well they're all seats whereas I can distinguish between Bob, Joe and Mary.

[razak olayinka]

Anytime you see anything like selection, that is talking about combination and anywhere you come across arrangement, that talks about permutation. I hope this helps! Good luck..

[femanan]

Thanks it does!