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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 ## Bob is training for a fitness competition. In order to ##### This topic has 3 expert replies and 1 member reply ### Top Member ## Bob is training for a fitness competition. In order to ## Timer 00:00 ## Your Answer A B C D E ## Global Stats Difficult Bob is training for a fitness competition. In order to increase his maximum number of pull-ups, he follows the following routine: he begins with 25 pull-ups, rests for thirty seconds, and then does 24 pull-ups and rests, dropping one pull-up each time (25, 24, 23, etc.) until his final set of 11 pull-ups. How many total pull-ups does Bob do? (A) 55 (B) 150 (C) 270 (D) 275 (E) 325 OA C Source: Magoosh ### GMAT/MBA Expert GMAT Instructor Joined 22 Aug 2016 Posted: 1459 messages Followed by: 27 members Upvotes: 470 BTGmoderatorDC wrote: Bob is training for a fitness competition. In order to increase his maximum number of pull-ups, he follows the following routine: he begins with 25 pull-ups, rests for thirty seconds, and then does 24 pull-ups and rests, dropping one pull-up each time (25, 24, 23, etc.) until his final set of 11 pull-ups. How many total pull-ups does Bob do? (A) 55 (B) 150 (C) 270 (D) 275 (E) 325 OA C Source: Magoosh We have a set of certain consecutive numbers in decreasing order. Set of # of pull-ups: {25, 24, 23, ..., 12, 11} The sum of the elements of the set can be found in many ways. I provide one of those ways. From 25 to 11, there are (25 - 11) + 1 = 15 numbers Average of the consecutive numbers from 11 to 25 = (11 + 25)/2 = 18 Thus, the sum of numbers from 11 to 25 = Total number of elements * Average of numbers = 15*18 = 270 pull-ups. The correct answer: C Hope this helps! -Jay _________________ Manhattan Review GMAT Prep Locations: New York | Bangkok | Abu Dhabi | Rome | and many more... Schedule your free consultation with an experienced GMAT Prep Advisor! Click here. ### Top Member Legendary Member Joined 29 Oct 2017 Posted: 609 messages Followed by: 4 members In order to find the total number of pull-ups that Bob does for the fitness competition, we need to find the sum of the numbers from 11 to 25. This can be done by subtracting the sum of the first 10 natural numbers from the sum of the first 25 natural numbers. $$\text{Sum: } \frac{25(26)}{2}-\frac{10(11)}{2}=325-55=270.$$ ### GMAT/MBA Expert Elite Legendary Member Joined 23 Jun 2013 Posted: 9836 messages Followed by: 490 members Upvotes: 2867 GMAT Score: 800 Hi All, We're told that Bob is training for a fitness competition. In order to increase his maximum number of pull-ups, he follows the following routine: he begins with 25 pull-ups, rests for thirty seconds, and then does 24 pull-ups and rests, dropping one pull-up each time (25, 24, 23, etc.) until his final set of 11 pull-ups. We're asked for the total number of pull-ups that Bob completes. This question can be solved in several different ways, including by 'bunching.' In simple terms, we are adding up all of the integers from 11 to 25, inclusive. Since there are 25 integers from 1 to 25 - and we are NOT including the first 10 integers, that means we are adding 25 - 10 = 15 individual numbers together. We can 'bunch' those numbers into seven groups of 2 and one left over number: 11 + 25 = 36 12 + 24 = 36 13 + 23 = 36 ... 17 + 19 = 36 and there's one number left over: an 18 Thus, we have 7(36) + 18 = 252 + 18 = 270 Final Answer: C GMAT assassins aren't born, they're made, Rich _________________ Contact Rich at Rich.C@empowergmat.com ### GMAT/MBA Expert GMAT Instructor Joined 25 Apr 2015 Posted: 1643 messages Followed by: 14 members Upvotes: 43 BTGmoderatorDC wrote: Bob is training for a fitness competition. In order to increase his maximum number of pull-ups, he follows the following routine: he begins with 25 pull-ups, rests for thirty seconds, and then does 24 pull-ups and rests, dropping one pull-up each time (25, 24, 23, etc.) until his final set of 11 pull-ups. How many total pull-ups does Bob do? (A) 55 (B) 150 (C) 270 (D) 275 (E) 325 The number of pull-ups Bob does is the sum of integers from 11 to 25, inclusive. Thus, the total number of pull-ups he does is 15 x (11 + 25)/2 = 15 x 18 = 270 Alternate Solution: The sequence of the integers from 11 to 25, inclusive, is an evenly-spaced set. Our goal is to find the sum of the set. We first determine the average value of this set: average = (smallest + largest)/2 = (11 + 25) /2 = 38/2 = 18 We also see that there are 25 - 11 + 1 = 15 integers in the set. We can now use the formula: sum = average x number sum = 18 x 15 = 270. 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