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02-05-2012, 10:08 PM
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#16 | | Senior Member
Join Date: Apr 2011 Location: Himmel
Posts: 2,071
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Originally Posted by pckeller The only time I have ever seen problems that "needed" combinatorics beyond the counting principle, the numbers involved were small enough to list. I'm thinking of that blue book problem about the plumber and the two apprentices. | I vividly recall that problem. Even that problem did not require combinatorics. Just use the counting principle on the two apprentices and divide by 2 because sending Tom and Bob the Plumber is the same as sending Bob and Tom.
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02-05-2012, 10:15 PM
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#17 | | Junior Member
Join Date: Dec 2011
Posts: 85
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Ok, a lot of you are making it really really complicated for most people who aren't geniuses. I'd just say there are 5 people, and you need to pick 3 specific ones... That makes 3/5, and it takes less than 10 seconds to think that through
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02-05-2012, 10:33 PM
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#18 | | Member
Join Date: Aug 2011 Location: Northern NJ
Posts: 907
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Ok, a lot of you are making it really really complicated for most people who aren't geniuses. I'd just say there are 5 people, and you need to pick 3 specific ones... That makes 3/5, and it takes less than 10 seconds to think that through
| Your logic is flawed. Perhaps you should think about your statement again.
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02-05-2012, 10:38 PM
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#19 | | Senior Member
Join Date: Apr 2011 Location: Himmel
Posts: 2,071
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^You tell him  !
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02-05-2012, 10:40 PM
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#20 | | Junior Member
Join Date: Dec 2011
Posts: 85
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Could you explain to me how it's flawed please
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02-05-2012, 10:41 PM
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#21 | | Junior Member
Join Date: Feb 2011 Location: Bronx, NY
Posts: 179
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Well, what if the question asked for 2 democrats and 1 republican instead? Would you still get 3/5?
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02-05-2012, 10:48 PM
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#22 | | Member
Join Date: Aug 2011 Location: Northern NJ
Posts: 907
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What if the question asked for 3 republicans?
You can't just attempt to put numbers together because they "work" once or twice.
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02-05-2012, 10:50 PM
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#23 | | Junior Member
Join Date: Dec 2011
Posts: 85
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It works in this situation because of the specific numbers chosen. It is not asking to pick all of one side. If the question was different I would choose another method.
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02-05-2012, 11:16 PM
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#24 | | Member
Join Date: Aug 2011 Location: Northern NJ
Posts: 907
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How about 2 democrats and 1 republican? Does that yield 3/5?
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02-06-2012, 06:27 AM
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#25 | | Junior Member
Join Date: Jan 2012
Posts: 80
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People often get confused from such problems because of the abundance of ways you can explain them. You can count with numbers, letters, whatever.
Learning the combination formula by far is the fastest way to solve these problems.Counting takes way too much time.
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02-06-2012, 07:48 AM
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#26 | | Junior Member
Join Date: Jan 2012
Posts: 121
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Originally Posted by risubu No, chung's. Hence the stupidity | I lol'd so hard after reading that. I'm trying to do his book right now, and it's taking me around 10 minutes to finish reading and solving one of his 50 tips. lol | |
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02-06-2012, 05:58 PM
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#27 | | Senior Member
Join Date: Jun 2010
Posts: 1,220
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Originally Posted by YoungProdigy I lol'd so hard after reading that. I'm trying to do his book right now, and it's taking me around 10 minutes to finish reading and solving one of his 50 tips. lol | I often contemplate the effectiveness of Chung's. I don't really see why the book was so highly recommended on CC. It's super hard, but I guess it makes you look at problems more in depth, such as the one I had posted originally.
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02-07-2012, 03:22 PM
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#28 | | Junior Member
Join Date: Jan 2012
Posts: 80
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I personally regret for not buying Chung's and Barron's guide but instead jumping on Gruber's and Barron's 2400 (which ,to me, looks like a brusquely cut version of the whole Barron's guide).
Even though I already attain 760-780 on Math, It took me month and a half to get from 400 to 760.This consists of 6-7 hours daily practice on both math and CR (tried to allot my time equally).
I guess if I bought those two in the first place, It would take me a week or two less to get the desired results (at least for math, CR is much more complex). But it's too late now ... I'll be attending institutional SAT on 24th Feb..all I can do is practice.
So choose your preparation materials wisely if you're out of time to prepare. ESPECIALLY if you're out of time to prepare.
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02-07-2012, 09:11 PM
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#29 | | Senior Member
Join Date: Jun 2010
Posts: 1,220
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^Thanks for the advice I'll be taking it in approximately one month.
I'm getting horribly off topic but I just have to know, what is "institutional SAT?"
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02-07-2012, 09:21 PM
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#30 | | Senior Member
Join Date: Apr 2011 Location: Himmel
Posts: 2,071
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^He probably means international SAT.
Anyway, this problem from Chung's is just out of left-field. The trickiest counting problem I've seen involved groups of people, and for people, remember that:
Jill and Jack = Jack and Jill.
Therefore, divide by the number of people in a group.
Example: How many ways can you send two of three plumbers to a job (Jill, Jack, and Rob).
3*2 = 6.
6/2 = 3 ways.
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