{"id":5712,"date":"2011-09-09T09:45:29","date_gmt":"2011-09-09T16:45:29","guid":{"rendered":"https:\/\/magoosh.com\/gre\/?p=5712"},"modified":"2012-01-23T18:45:39","modified_gmt":"2012-01-24T02:45:39","slug":"gre-probability-questions-using-the-elimination-strategy","status":"publish","type":"post","link":"https:\/\/magoosh.com\/gre\/gre-probability-questions-using-the-elimination-strategy\/","title":{"rendered":"GRE Probability Questions: Using the Elimination Strategy"},"content":{"rendered":"

In my last post<\/a>, we examined the following question.<\/p>\n

From a group of 5 managers (Joon, Kendra, Lee, Marnie and Noomi), 2 people are randomly selected to attend a conference in Las Vegas.\u00a0 What is the probability that Marnie and Noomi are both<\/span> selected? <\/strong><\/p>\n

(A) 0.1<\/strong><\/p>\n

(B) 0.2<\/strong><\/p>\n

(C) 0.25<\/strong><\/p>\n

(D) 0.4 <\/strong><\/p>\n

(E) 0.6<\/strong><\/p>\n

In that post, we used our intuition to eliminate two answer choices (D and E) in a matter of seconds. In this post, we\u2019ll use another elimination technique to help further reduce the number of answer choices to guess from.<\/p>\n

To begin, let\u2019s review the standard probability formula. It says that, if we have an experiment where each outcome is equally likely to occur, then:<\/p>\n

P(A) = [# of outcomes where A occurs]\/[total # of outcomes]<\/strong><\/p>\n

So, P(Marnie and Noomi are both selected)= [# of outcomes where they are both selected]\/[total # of outcomes]<\/p>\n

If we use this formula, it\u2019s always best to calculate the denominator first. The reason for this is twofold:<\/p>\n

1)\u00a0\u00a0 Calculating the denominator is typically easier than calculating the numerator. So, if we calculate the denominator first, we may gain some insight into how to calculate the numerator.<\/p>\n

2)\u00a0\u00a0 Calculating the denominator can help us quickly eliminate answer choices.<\/p>\n

For the denominator in the above question, we need to determine the number of outcomes when 2 people are selected from a group of 5 people. Since the order of the selected people does not matter, this is a combination question. So, we can select 2 people from 5 people in 5<\/sub>C2<\/sub> ways. When we apply the combination formula, we see that 5<\/sub>C2<\/sub>= 10<\/strong>. This means that:<\/p>\n

P(Marnie and Noomi are both selected)= [# of outcomes where they are both selected]\/[10<\/strong>]<\/p>\n

Now that we know the denominator equals 10, we can conclude that the probability cannot be 0.25, since it is impossible for a fraction with denominator 10 to equal 0.25<\/p>\n

So, by calculating the denominator, we were able to eliminate one more answer choice.<\/p>\n

At this point, we have quickly eliminated 3 answer choices (C, D and E), leaving us with a 50-50 chance of guessing the correct answer. Not bad if we don\u2019t know how to solve the question.<\/p>\n

In the next post<\/a>, we\u2019ll examine two different ways to solve the question.<\/p>\n","protected":false},"excerpt":{"rendered":"

In my last post, we examined the following question. From a group of 5 managers (Joon, Kendra, Lee, Marnie and Noomi), 2 people are randomly selected to attend a conference in Las Vegas.\u00a0 What is the probability that Marnie and Noomi are both selected? (A) 0.1 (B) 0.2 (C) 0.25 (D) 0.4 (E) 0.6 In […]<\/p>\n","protected":false},"author":11,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[39,25],"tags":[],"ppma_author":[12266],"class_list":["post-5712","post","type-post","status-publish","format-standard","hentry","category-data-analysis","category-math"],"acf":[],"yoast_head":"\nGRE Probability Questions: Using the Elimination Strategy - Magoosh Blog \u2014 GRE\u00ae Test<\/title>\n<meta name=\"description\" content=\"In this post, Brent Hanneson shows you how to use the elimination strategy to solve the GRE probability questions.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/magoosh.com\/gre\/gre-probability-questions-using-the-elimination-strategy\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"GRE Probability Questions: Using the Elimination Strategy\" \/>\n<meta property=\"og:description\" content=\"In this post, Brent Hanneson shows you how to use the elimination strategy to solve the GRE probability questions.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/magoosh.com\/gre\/gre-probability-questions-using-the-elimination-strategy\/\" \/>\n<meta property=\"og:site_name\" content=\"Magoosh Blog \u2014 GRE\u00ae Test\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/Magoosh\/\" \/>\n<meta property=\"article:published_time\" content=\"2011-09-09T16:45:29+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2012-01-24T02:45:39+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/magoosh.com\/gre\/files\/2016\/09\/Magoosh-Facebook-Default-Pic.png\" \/>\n\t<meta property=\"og:image:width\" content=\"1200\" \/>\n\t<meta property=\"og:image:height\" content=\"628\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"author\" content=\"Brent\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@MagooshGRE\" \/>\n<meta name=\"twitter:site\" content=\"@MagooshGRE\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Brent\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"2 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/magoosh.com\/gre\/gre-probability-questions-using-the-elimination-strategy\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/magoosh.com\/gre\/gre-probability-questions-using-the-elimination-strategy\/\"},\"author\":{\"name\":\"Brent\",\"@id\":\"https:\/\/magoosh.com\/gre\/#\/schema\/person\/b2fbd67daad89818fde8859916e23409\"},\"headline\":\"GRE Probability Questions: Using the Elimination Strategy\",\"datePublished\":\"2011-09-09T16:45:29+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/magoosh.com\/gre\/gre-probability-questions-using-the-elimination-strategy\/\"},\"wordCount\":373,\"commentCount\":2,\"publisher\":{\"@id\":\"https:\/\/magoosh.com\/gre\/#organization\"},\"articleSection\":[\"GRE Data Analysis\",\"GRE Math\"],\"inLanguage\":\"en-US\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/magoosh.com\/gre\/gre-probability-questions-using-the-elimination-strategy\/\",\"url\":\"https:\/\/magoosh.com\/gre\/gre-probability-questions-using-the-elimination-strategy\/\",\"name\":\"GRE Probability Questions: Using the Elimination Strategy - 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