• NEW! FREE Beat The GMAT Quizzes
Hundreds of Questions Highly Detailed Reporting Expert Explanations
• 7 CATs FREE!
If you earn 100 Forum Points

Engage in the Beat The GMAT forums to earn
100 points for 49 worth of Veritas practice GMATs FREE VERITAS PRACTICE GMAT EXAMS Earn 10 Points Per Post Earn 10 Points Per Thanks Earn 10 Points Per Upvote ## schistosomiasis and malaria. ##### This topic has 1 expert reply and 4 member replies ## schistosomiasis and malaria. In a certain population, the two most heavily diagnosed diseases are schistosomiasis and malaria. Over the past five years, malaria has accounted for more than half of all disease cases, and schistosomiasis, which accounted for 40% of all disease cases in the community five years ago, accounted for 30% in the past year. Which of the following must be true on the basis of the statements above? A) There were fewer cases of schistosomiasis last year than five years ago. B) The percentage of disease cases from malaria has increased over the past 5 years. C) Some disease has experienced an increase in the number of its total cases, as long as the total number of disease cases went down by a number less than 30%. D) Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis. E) If the total number of schistosomiasis cases increased over the past five years, then the total number of disease cases must have increased by more than 30%. ### GMAT/MBA Expert GMAT Instructor Joined 25 May 2010 Posted: 15385 messages Followed by: 1872 members Upvotes: 13060 GMAT Score: 790 Top Reply Mo2men wrote: himu wrote: In a certain population, the two most heavily diagnosed diseases are schistosomiasis and malaria. Over the past five years, malaria has accounted for more than half of all disease cases, and schistosomiasis, which accounted for 40% of all disease cases in the community five years ago, accounted for 30% in the past year. Which of the following must be true on the basis of the statements above? A) There were fewer cases of schistosomiasis last year than five years ago. B) The percentage of disease cases from malaria has increased over the past 5 years. C) Some disease has experienced an increase in the number of its total cases, as long as the total number of disease cases went down by a number less than 30%. D) Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis. E) If the total number of schistosomiasis cases increased over the past five years, then the total number of disease cases must have increased by more than 30%. Dear GMATGuru, Could you please help with this question? Thanks M --> more than 50% of all disease cases over the past 5 years S --> 40% of all disease cases 5 years ago, 30% of all disease cases now For each answer choice: Try to devise a case that aligns with the information in the passage but CONTRADICTS the answer choice, thus proving that the answer choice does NOT have to be true. A: There were fewer cases of schistosomiasis last year than five years ago. 5 years ago:' Total disease cases = 10 S = 40% of 10 = 4 Now: Total disease cases = 100 S = 30% of 100 = 30 Since there are more S cases now than there were 5 years ago, A does not have to be true. Eliminate A. B: The percentage of disease cases from malaria has increased over the past 5 years. 5 years ago: M = 55% Now: M = 51% Thus, B does not have to be true. Eliminate B. C: Some disease has experienced an increase in the number of its total cases, as long as the total number of disease cases went down by a number less than 30%. 5 years ago:' Total disease cases = 100 S = 40% of 100 = 40 M = 58% of 100 = 58 Other = 2% of 100 = 2 Now: Total disease cases = 80' S = 30% of 80 = 24 M = 70% of 80 = 56 Other = 0 Here, no disease experiences an increase in the number of cases, illustrating that C does not have to be true. Eliminate C. D: Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis. Annual percentages for M and S over the past 5 years: M: 51%, 39%, 60%, 60%, 70% S: 40%, 40%, 30%, 30%, 30% The values in red illustrate that D does not have to be true. Eliminate D. The correct answer is E. E: If the total number of schistosomiasis cases increased over the past five years, then the total number of disease cases must have increased by more than 30%. 5 years ago: Total disease cases = 100 S = 40% of 100 = 40 Now: Total disease cases = 130 S = 30% of 130 = 39 Here, the total number of disease cases increases by exactly 30%, with the result that the total number of S cases DECREASES from 40 to 39. Implication: For the total number of S cases to INCREASE, the total number of disease cases must increase by MORE THAN 30%. Thus, E must be true. _________________ Mitch Hunt Private Tutor for the GMAT and GRE GMATGuruNY@gmail.com If you find one of my posts helpful, please take a moment to click on the "UPVOTE" icon. Available for tutoring in NYC and long-distance. For more information, please email me at GMATGuruNY@gmail.com. Student Review #1 Student Review #2 Student Review #3 Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now. Senior | Next Rank: 100 Posts Joined 22 Jul 2012 Posted: 30 messages Upvotes: 5 IMO E A) There were fewer cases of schistosomiasis last year than five years ago. - Population not known so number cannot be accounted B) The percentage of disease cases from malaria has increased over the past 5 years. - Cant Say - May have been steady C) Some disease has experienced an increase in the number of its total cases, as long as the total number of disease cases went down by a number less than 30%. Let us say Malaria was 26 in a population of 50. Schistosomiasis was 15 and another disease say Hepatitis was earlier 8 and now has 9 cases in last year. However, we still dont know what was the incidence of Schistosomiasis 2 or 3 years ago so cannot compare and confirm new disease case increase. D) Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis. - We know that over last 5 years malaria has been more than 50%. But we dont know whether in each year it has been dominant. In one year it may account 90%, in the next 40% and cannot be compared to Schistosomiasis. E) If the total number of schistosomiasis cases increased over the past five years, then the total number of disease cases must have increased by more than 30%. - Yes. There are 2 conditions. Malaria accounts for more than 50% and Schistosomiasis last year was 30% earlier 40%. If in past years it has been increasing in number, can be only if the disease cases have increased > 30%. Consider number of disease cases before 5 years, 100. Schistosomiasis cases - 40. If the number remains constant, Cases for Schistosomiasis in past 5 years = 500 - Malaria cases (5 * 51) = 500-255 =245 . If cases are increasing, they have to go 41-42-43-44-45 (but last year the cases were only 30%. That means 45 is 30% of a value = 150. From initial disease cases, this number is 50% higher. Proven! Master | Next Rank: 500 Posts Joined 21 Dec 2008 Posted: 345 messages Followed by: 3 members Upvotes: 6 You are correct Senior | Next Rank: 100 Posts Joined 22 Jul 2012 Posted: 30 messages Upvotes: 5 WoW! nice to know. Thanks Himu for posting a good question! Regards, Sonali. ### Top Member Legendary Member Joined 25 Sep 2015 Posted: 690 messages Followed by: 5 members Upvotes: 14 himu wrote: In a certain population, the two most heavily diagnosed diseases are schistosomiasis and malaria. Over the past five years, malaria has accounted for more than half of all disease cases, and schistosomiasis, which accounted for 40% of all disease cases in the community five years ago, accounted for 30% in the past year. Which of the following must be true on the basis of the statements above? A) There were fewer cases of schistosomiasis last year than five years ago. B) The percentage of disease cases from malaria has increased over the past 5 years. C) Some disease has experienced an increase in the number of its total cases, as long as the total number of disease cases went down by a number less than 30%. D) Each year over the past five, malaria has accounted for a larger percentage of disease cases than schistosomiasis. E) If the total number of schistosomiasis cases increased over the past five years, then the total number of disease cases must have increased by more than 30%. Dear GMATGuru, Could you please help with this question? Thanks • 5-Day Free Trial 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code • Free Veritas GMAT Class Experience Lesson 1 Live Free Available with Beat the GMAT members only code • Get 300+ Practice Questions 25 Video lessons and 6 Webinars for FREE Available with Beat the GMAT members only code • 1 Hour Free BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Magoosh Study with Magoosh GMAT prep Available with Beat the GMAT members only code • Free Practice Test & Review How would you score if you took the GMAT Available with Beat the GMAT members only code • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • Award-winning private GMAT tutoring Register now and save up to200

Available with Beat the GMAT members only code

• 5 Day FREE Trial
Study Smarter, Not Harder

Available with Beat the GMAT members only code

• FREE GMAT Exam
Know how you'd score today for \$0

Available with Beat the GMAT members only code

### Top First Responders*

1 Ian Stewart 43 first replies
2 Brent@GMATPrepNow 35 first replies
3 Scott@TargetTestPrep 33 first replies
4 Jay@ManhattanReview 28 first replies
5 GMATGuruNY 19 first replies
* Only counts replies to topics started in last 30 days
See More Top Beat The GMAT Members

### Most Active Experts

1 Scott@TargetTestPrep

Target Test Prep

149 posts
2 Max@Math Revolution

Math Revolution

93 posts
3 Brent@GMATPrepNow

GMAT Prep Now Teacher

53 posts
4 Ian Stewart

GMATiX Teacher

52 posts
5 GMATGuruNY

The Princeton Review Teacher

32 posts
See More Top Beat The GMAT Experts