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bpolley00
- Master | Next Rank: 500 Posts
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- Joined: Wed Jul 11, 2012 5:04 pm
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- GMAT Score:650
Hey everyone, so far I have really struggled with Permutations, Combinations and Anagrams. Thus, I was hoping to get a forum post that was completely devoted to not only answering these questions but also doing so efficiently. In addition, I was hoping to be able to get an explanation on distinguishing these types of questions on the test. So my goal for this post is to go over what I have as far as study materials and to see if I cannot get Ron or some other expert to verify/ elaborate further, in a more concise manner.
Anagrams- These questions are usually asking for arrangements. So for example, how many arrangements of 6 books on a shelf can you make? The answer is merely 6! = 720. If you have a question that asks how many combinations of Pizzazzz can you make it would be 8!( Total number of letters)/ 5! (repeated Letters) =8*6*7=336. Another Example would be Atlanta= 7!/3!2! Which I will let you guys figure out.
Coin Flip Questions- Get K Flips out of N Flips. So what is probability that you get 3 heads out of 4 flips? The equation I have is NCK/2^n Where NCK= N!/k!(N-K)! So for this question you would have NCK= 4!/3!1!= 4 4/ 2^4= 4/16 = 1/4
Combinations- are known as unordered subgroups where basically order doesn't matter. Thus, I merely have the NCK equation So N!/K!(N-K)! Which is very similar to the coin flip.
Hard Question: A Volcano has a 50% probability in a year to erupt. What is the probability that it erupts 2 years in a 5 year period? The only way i know to solve this is with the Binomial Distribution Formula = NCK*p^k * (1-p)^(n-K)
I watched the Thursday with Ron on the Slot Method; However, I didn't really quite get it with the order does matter vs order doesn't matter.
Basically, I just need a summation of someone who is getting 100% of these questions correct to give me an explanation of exactly what approach you are taking per different questions and how you are distinguishing which approach to use, as I feel that my approach is quite formula heavy and not very intuitive.
Thanks so much for taking the time to read my post guys and I look forward to hearing your responses.
Anagrams- These questions are usually asking for arrangements. So for example, how many arrangements of 6 books on a shelf can you make? The answer is merely 6! = 720. If you have a question that asks how many combinations of Pizzazzz can you make it would be 8!( Total number of letters)/ 5! (repeated Letters) =8*6*7=336. Another Example would be Atlanta= 7!/3!2! Which I will let you guys figure out.
Coin Flip Questions- Get K Flips out of N Flips. So what is probability that you get 3 heads out of 4 flips? The equation I have is NCK/2^n Where NCK= N!/k!(N-K)! So for this question you would have NCK= 4!/3!1!= 4 4/ 2^4= 4/16 = 1/4
Combinations- are known as unordered subgroups where basically order doesn't matter. Thus, I merely have the NCK equation So N!/K!(N-K)! Which is very similar to the coin flip.
Hard Question: A Volcano has a 50% probability in a year to erupt. What is the probability that it erupts 2 years in a 5 year period? The only way i know to solve this is with the Binomial Distribution Formula = NCK*p^k * (1-p)^(n-K)
I watched the Thursday with Ron on the Slot Method; However, I didn't really quite get it with the order does matter vs order doesn't matter.
Basically, I just need a summation of someone who is getting 100% of these questions correct to give me an explanation of exactly what approach you are taking per different questions and how you are distinguishing which approach to use, as I feel that my approach is quite formula heavy and not very intuitive.
Thanks so much for taking the time to read my post guys and I look forward to hearing your responses.
