![\"Manhattan](\"https:\/\/www.manhattanprep.com\/gmat\/wp-content\/uploads\/sites\/18\/2018\/10\/gmat-official-guide-2019-edition-part-2-stacey-koprince.png\")
<\/p>\n<\/p>\n
Here we go, here we go! Welcome to part 2 of a little series on the GMAT Official Guide 2019 edition, hot off the presses; if you\u2019d like, you can start with the first installment<\/a> of this article series. Today\u2019s post focuses on Data Sufficiency.<\/span><\/p>\n There are 26 new Data Sufficiency (DS) problems (and 26 were dropped). <\/span><\/p>\n As we saw for Problem Solving, most of the new problems are on the easier to medium side. There are still some quite hard older problems, but the fact that there aren\u2019t many new hard ones for the second year in a row leads me to believe that we should expect to hear an announcement in the not-too-distant future about some new hard-question product (or perhaps that an online product has had more hard questions added to it?). If so, I\u2019m looking forward to it!<\/span><\/p>\n Six of the new problems are about statistics\u2014some easier ones around average and median, including one that had some really clever wording (#326) and another that tested standard deviation in a way that I don\u2019t recall seeing before on published official questions (#290). More on both of those below.<\/span><\/p>\n Ratios are also covered in 6 new problems, most of which are on the easier side. And we can toss in a 7<\/span>th<\/span>, harder problem that’s about probability at a high level\u2026but you really need to understand ratios in order to be able to solve.<\/span><\/p>\n Anecdotally, I\u2019ve noticed that students in my classes tend to struggle with ratios\u2014it\u2019s not something we tend to see in obvious ways in the real world, even in quant-focused jobs. But understanding how ratios work can actually be really valuable in the business world, so I recommend spending some of your precious study time making sure you understand how the fundamentals work here.<\/span><\/p>\n Again anecdotally speaking, my students who have struggled with ratios have told me they really like the \u201cratio table\u201d we introduce in our Foundations of Math strategy guide\u2014so check that out if you need a little work here. (See the Fractions, Decimals, Percents, & Ratios chapter\u2014look for the stuff labeled Ratios at the end of the chapter.)<\/span><\/p>\n I didn\u2019t spot any other big trends in the remaining new problems, but I did quite like #301.<\/span><\/p>\n Want to try the three that I\u2019ve mentioned? Try them on your own first: #290, #301, and #326. I\u2019ll give some hints below, then talk about how I solved each one.<\/span><\/p>\n As before, I can\u2019t repeat the full text of the problems for copyright reasons\u2014you\u2019ll need to get the book\u2026or at least go view these problems in the \u201cLook Inside\u201d feature on Amazon. (Note that you can only look at a small number of pages in any one book\u2026so you can\u2019t just use that feature to do the whole GMAT Official Guide 2019 edition without paying for it. Besides, they do work hard to produce these problems\u2014so we should pay for something that\u2019s of good value. <\/span>\u263a<\/span>)<\/span><\/p>\n If you want to use the Amazon search function, look up this book, click on the Look Inside link, and then use the following search terms (do use the quotes for the ones that have more than one word):<\/span><\/p>\n #290 \u201chistory class\u201d<\/span><\/p>\n #301 Shana<\/span><\/p>\n #326 \u201c9 of the 20 houses\u201d<\/span><\/p>\n #290:<\/b> What is standard deviation a measure of? What about mean\u2014what does that mean? (Pun intended\u2026 ?<\/span>) <\/span><\/p>\n #301:<\/b> \u201cLess than\u201d 48. That\u2019s interesting.<\/span><\/p>\n #326:<\/b> \u201cMore than 9 of the 20\u201d?? That\u2019s super-interesting wording.<\/span><\/p>\n #290:<\/b> The question asks for the <\/span>maximum<\/span><\/i>. Can you come up with multiple scenarios that fit the facts in the statements but provide different possible maximum scores?<\/span><\/p>\n #301:<\/b> Don\u2019t try to write equations. Pretend you\u2019re Shana, in the bookstore, and you\u2019ve got $47.99 in your pocket. You\u2019re trying to figure out whether you can afford these three books. How are you going to figure that out?<\/span><\/p>\n #326:<\/b> \u201cMore than 9\u201d is the same thing as \u201cat least 10.\u201d Out of 20. And statement 2 mentions <\/span>median<\/span><\/i>.<\/span><\/p>\n #290:<\/b><\/p>\n The question stem doesn’t give us much\u2014there are 10 students, so there are 10 scores in the mix. What\u2019s the maximum score? No idea, but the fact that they\u2019re asking for a <\/span>maximum<\/span><\/i> already signals to me that I\u2019m likely going to need to test cases on this problem. Let\u2019s go take a look at the statements. <\/span><\/p>\n Knowing that the mean (average) score was 75 leaves open various possibilities. For instance, all 10 students could have scored 75. Or half of the students could have scored 70 and the other half could have scored 80.<\/span><\/p>\n See what we just did there? We tested two possible cases. Each case used the given information (10 students total, mean score of 75) but we came up with two different possible maximum scores, so the first statement is not sufficient to answer the question. Eliminate answers (A) and (D).<\/span><\/p>\n What about statement (2)? Standard deviation is a measure of the spread of the numbers. The closer together the numbers are, the smaller the standard deviation; the more spread out the numbers, the broader the standard deviation.<\/span><\/p>\n First, remember that you\u2019re supposed to forget statement (1) right now. If I only know the standard deviation but nothing at all about the scoring scale used (is it 1 to 10? 0 to 100??), I can\u2019t say what the maximum score was. By itself, statement (2) is not sufficient; eliminate answer (B).<\/span><\/p>\n What if we put the two statements together? Maybe this means the maximum score is 75 + 5 = 80?<\/span><\/p>\n It doesn\u2019t, actually. The calculation for standard deviation is super complicated, and the official explanation\u2014which tests cases, too\u2014gets into some\u2026crazy calculations. So I\u2019m just going to tell you something that you\u2019ll know forever. If I tell you (1) the number of data points in a set, (2) the average value of those data points, and (3) the standard deviation of those points\u2026then you cannot figure out the range of possible values, or the smallest or largest value, of the data points in that set. Lots of combinations are possible.<\/span><\/p>\n Well, there is one exception: if the standard deviation is 0, then you can\u2014because when the SD is 0, then every data point in the set has to be the same (and, therefore, the average is also equal to the value of each data point).<\/span><\/p>\n The correct answer is (E).<\/span><\/p>\n #301:<\/b><\/p>\n Look at the statements. They never give us real values for the prices of the books\u2014it\u2019s always either \u201cless than\u201d or one price relative to another price. So test cases here.<\/span><\/p>\n The most expensive book costs \u201cless than $17.\u201d For the sake of not driving yourself crazy, pretend the thing cost exactly $17. If you bought 3 books at that price, how much would you spend?<\/span><\/p>\n (17)(3) = 51, which is over your $48 budget. Now, the book was \u201cless than 17\u201d but that means your three books could\u2019ve been $16.99, $16.98, and $16.97, which is around $51 (i.e., over budget). Or the books could have been $4, $5, and $6, in which case you have enough money left over to take me out to lunch. Yay!\u00a0?<\/span><\/p>\n I can\u2019t tell whether Shana spent less than $48, so statement (1) is not sufficient; eliminate answers (A) and (D).<\/span><\/p>\n What about statement (2)? Here\u2019s where my second hint comes in. Do <\/span>not<\/span><\/i> start to assign variables and write equations and ugh. Whip out an envelope and a pen\u2014we\u2019re going to do some back-of-the-envelope checks on these numbers.<\/span><\/p>\n The cheapest one was $3 less than the second most expensive. So I could have spent, say, $3, $6, and $7\u2014coming in under my $48 budget. Or I could have spent, say, $50, $53, and $100\u2014totally blowing my budget. Nope, this statement\u2019s not sufficient either; eliminate answer (B).<\/span><\/p>\n Put them together. The most expensive has to be under $17. (Which is annoying, so let\u2019s just call it $17 and remember to take off 1 penny at the end.)<\/span><\/p>\n The second most expensive has to be at least a penny less than the most expensive, which is annoying, so let\u2019s just call it $17 and remember to take off 2 pennies at the end.<\/span><\/p>\n And then the cheapest one is $3 less than that, so\u2026$14 minus another two pennies.<\/span><\/p>\n Oh, wait. This is interesting. So in my first test, I did (17)(3) = 51. Which is the same as 17 + 17 + 17 = 51.<\/span><\/p>\n Now, I\u2019ve got 17 + 17 + 14\u2026which is 3 less, or 48. Oh\u2026and then I need to take off a few more pennies. Wow! Shana did indeed spend less than $48 on her three books.<\/span><\/p>\n Statements (1) and (2) together are sufficient to answer the question. The correct answer is (C).<\/span><\/p>\n #326:<\/b><\/p>\n The question stem already mentions the concept of average and then asks that really weird \u201cmore than 9 of the 20\u201d thing. More than 9 is the same thing as \u201cat least 10\u201d and they\u2019ve already brought up statistics, so now I\u2019m wondering whether they\u2019re getting at something around median and I\u2019m scanning the statements and\u2026boom! Yes, statement (2) says something about median.<\/span><\/p>\n If I have 20 numbers in a set, which ones do I use to calculate median? 20 numbers = annoying, so let\u2019s make this easier. If I have 6 numbers in the set, then I need to know (counting on my fingers here) numbers 3 and 4 in the set\u2014those are the middle two. Number 3 is half of number 6 and 4 is just the next one up. So apply that pattern to the number 20: the number 10 is half and then I need to go one up to 11. I need 10 and 11\u2026haha, that\u2019s why they specified \u201cmore than 9.\u201d Because 10 and 11 are the relevant numbers for the median.<\/span><\/p>\n Okay, what else do I know? The average is $160k and there are 20 houses total, so I can find the sum if I want to (since average = sum \/ # of terms).<\/span><\/p>\n And what is the question really asking? Was house price #10 (if I were to write the numbers in increasing order) less than the average? Or was at least one half of the calculation for the median less than the average?<\/span><\/p>\n Let\u2019s find out!<\/span><\/p>\n Statement (1) tells me the price of the most expensive house, or #20 on the list if I write them in increasing order\u2026and that is totally useless when I\u2019m trying to figure out something about the #10 house. This one isn\u2019t sufficient; eliminate answers (A) and (D).<\/span><\/p>\n Okay, statement (2)\u2026the median was $150k. How do I calculate median again? Oh, right, find the average of houses #10 and #11. And remember that #10 has to be less than #11\u2014since we\u2019re doing median, which means they have to be written in increasing order. So the median is the average of just these two houses\u2026and that median is only $150k\u2026so house #10\u2019s price had to be less than $150k.<\/span><\/p>\n And that\u2019s less than the overall overage of $160k, so yes, at least 10 of the houses had prices that were less than $160k. Sufficient!<\/span><\/p>\n The correct answer is (B).<\/span><\/p>\n How are you feeling? Ready for a change of pace? Let\u2019s move on to Verbal\u2014join me next time<\/a> for a rundown of the Verbal sections of the new GMAT Official Guide 2019 edition.\u00a0?<\/span><\/p>\n Can\u2019t get enough of Stacey\u2019s GMAT mastery? Attend the first session of one of\u00a0her upcoming GMAT courses<\/a>\u00a0absolutely free, no strings attached. Seriously.<\/strong><\/em><\/p>\n Here we go, here we go! Welcome to part 2 of a little series on the GMAT Official Guide 2019 edition, hot off the presses; if you\u2019d like, you can start with the first installment of this article series. Today\u2019s post focuses on Data Sufficiency.<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[15,873,929,874,52871,930,2,52877,52945,8],"tags":[53602],"yst_prominent_words":[54403,54416,54413,54414,54417,54415,54411,54401,54398,54396,54395,54402,54400,54418,54127,54399,54397,54410,54310,54412],"class_list":["post-16375","post","type-post","status-publish","format-standard","hentry","category-data-suff","category-for-current-studiers","category-gmat-prep","category-gmat-resources","category-gmat-strategies","category-gmat-study-guide","category-how-to-study","category-in-the-news","category-products-and-services","category-quant-on-gmat","tag-gmat-official-guide-2019-edition"],"_links":{"self":[{"href":"https:\/\/www.manhattanprep.com\/gmat\/wp-json\/wp\/v2\/posts\/16375","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.manhattanprep.com\/gmat\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.manhattanprep.com\/gmat\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.manhattanprep.com\/gmat\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.manhattanprep.com\/gmat\/wp-json\/wp\/v2\/comments?post=16375"}],"version-history":[{"count":4,"href":"https:\/\/www.manhattanprep.com\/gmat\/wp-json\/wp\/v2\/posts\/16375\/revisions"}],"predecessor-version":[{"id":16975,"href":"https:\/\/www.manhattanprep.com\/gmat\/wp-json\/wp\/v2\/posts\/16375\/revisions\/16975"}],"wp:attachment":[{"href":"https:\/\/www.manhattanprep.com\/gmat\/wp-json\/wp\/v2\/media?parent=16375"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.manhattanprep.com\/gmat\/wp-json\/wp\/v2\/categories?post=16375"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.manhattanprep.com\/gmat\/wp-json\/wp\/v2\/tags?post=16375"},{"taxonomy":"yst_prominent_words","embeddable":true,"href":"https:\/\/www.manhattanprep.com\/gmat\/wp-json\/wp\/v2\/yst_prominent_words?post=16375"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}What\u2019s New in Data Sufficiency for the GMAT Official Guide 2019 Edition?<\/b><\/h4>\n
If you\u2019re stuck, here are some hints. But promise me: Don\u2019t look until you really need to!<\/b><\/h4>\n
Need another hint? Here you go.<\/b><\/h4>\n
Solutions<\/b><\/h4>\n
\n
\n![\"stacey-koprince\"](\"https:\/\/cdn2.manhattanprep.com\/gmat\/wp-content\/uploads\/sites\/18\/2015\/06\/stacey-koprince-150x150.png\")
<\/a>Stacey Koprince<\/a>\u00a0is a Manhattan Prep instructor based in Montreal, Canada and Los Angeles, California.<\/strong>\u00a0Stacey has been teaching the GMAT, GRE, and LSAT for more than 15 years and is one of the most well-known instructors in the industry. Stacey loves to teach and is absolutely fascinated by standardized tests.\u00a0Check out Stacey\u2019s upcoming GMAT courses here<\/a>.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"