stucco005

Good catch siddith

2. First Distance = Second Distance Time1*Speed1 = Time2*Speed2 4*Speed1 = 2*Speed2 2*Speed1 = Speed2 Pick Speed1 = 26 (in range). Thus, Speed2 = 52 (also in range). So, Distance1 = 26*4 = 104. Hmmm, this fits the description, but it is not among the answer choices, so must increase the speed. Try Speed1 = 29, So Speed2 = 58 Now, 4*29 = 116. Ans A. Note, that it cannot be B because that would require Speed2 = 60mph, and the range is BETWEEN (not inclusive) 45 and 60.

The key is that these integers are "consecutive". From that simply do a weighted average to figure out what the average (and median in this case) is. From that, you'll be able to determine what the entire list of numbers is.

A is the correct answer. Simply because if the BF portion is not the conclusion, then what is?

The correct answer is B. If it is true that the predictions could be made by other means, it would show that perhaps the predictor is not that special in predicting her fortunes, that in fact she gets it from somewhere else.

Perfect! Thanks

What if I asked you to find the average weight of 7 poeple, 5 of whom weigh an average of 175 lbs and the other 2 whom weigh an average of 300 lbs? How would you set up and solve that equation? Here's how: [5(175) + 2(300)]/7 = 1475/7 ~ 210 Now apply that same concept here: Let D = the number of directors. Likewise, let M = number of managers Let A = the average of salary of both D and M So, Using (1) and (2) together (and remembering the above example) we get: [(15000 + A)D + (A - 5000)M]/(D + M) = A 15000D + DA + MA - 5000M = DA + MA 15000D = 5000M 3D = M. So, remeber our original desire was to solve D/(D + M)? Then just substitue M for 3D and get D/(D + 3D) = D/4D = 1/4. Ans C.

Please provide a detailed explination. Thanks! Ok, Since no one is answering my question I will attempt to do so by looking at the information given in the stem. Since the battery lives are symmetric about the mean, then that means that all values are equi distance from one another. For example, lets say 50 is the mean and 2 is the distance, then we could have: ....46 48 50 52 54... Now looking at the how the numbers relate (and knowing the answer!) it appears that for standard deviations which involve equi distances from the mean that one devaition below and one deviation above divides symettrially the distribution above and below. Thus, you can get the answer by using both (1) and (2) (1) tells you that 68 percent of the distribution is one deviation above and below the mean. That means 32 percent of the distribution remains for the top and the bottom, thus 32/2 = 16 percent exists in both top and bottom halfs. (2) tells you that 16% exists in the bottom half. Since we are dealing with the symetric properites of the equation this means the top half is also 16%. Anybody want to 2nd/challege that?

If you take a = 2, and b = 3. The coordinates are (-2, 3) and (-3, 2), which are in the same quadrant. Notice that the negative sign always stays with the X coordinate.

In data suff questions, work out an equation or target the answer before diving into the additional data. 1. Let M = manager, D = director Needed: D/(D + M) (1) INSUFF, no information about D. (2) INSUFF, no information about M. (1) and (2): Setup and equation for the averages: 15000D + (-5000M)/[M+D] = 0 Note: use 0 as the average since the data specifies above and below. Solve to get: 1D to 3M, thus the percent of directors to managers is (1 director)/(4 total) 2. This is a Venn Diagram question, and is best solved by drawing such a diagram and filling in the values. An equation for this type of problem is: Total = All_Group1 + All_Group2 - Both + Neither. In this problem, the stem tells us that "each of the 128 people attended" so we can throw out the "Neither" portion of the formula above, and are left with: 128 = Morning_People + AfterNoon_People - Both. Now, the trick is to recognize that both the Morning_People value and the AfterNoon_People value contain the Both value. (That is why you must subtract the Both value so you can eliminate that value when the two Group values overlap). (1) INSUFF: Only tells you the Both parameter in the question. (2). SUFF: This tells you that: AfterNoon_People_ONLY + Both = (7/8), thus (1/8) = Morning_People_ONLY. So the answer is (1/8)128

That value pair was only intended as an extreme value for (1) in order to create a YES case for m > 3z. When (1) and (2) are combined you will have readjust your extremes.

Hey guys, I agree with the OA. If m is some integer and m/3 has two different prime factors then that simply means that m has 3 prime factors. Namely, 3 and the other two prime factors mentioned in (2). Thus, answer B is sufficient.

(thousands)(hundreds)(tens)(units).(tenths)(hundredths)(thousandths)

I do not go by any rigid rules, but I do use extremes. By extremes I mean values that can cause the inequalities to change. A checklist could be 0, values between -1 and 1 (decimal values) -ve and +ve values. (Generally large numbers in either direction) Generally you can tell from the problem what values would be approriate. For an example, I'll answer your second question above: Simplify: m > -z ? (1) Simplify: m > 3z Go through checklist: Assume: m=100,z=1 (YES), m=0; z=-1 (NO) INSUFF. (2) Simplify: 4z > m Go through checklist: Assume: m=2, z=1 (YES); m=-5, z=-1 (NO) INSUFF. NOW, add both equations to get z > 0 Since z > 0, go back through all the value pair sets above and strike out the value pairs that have z -z remain. Ans C.

For plugging in with inequalities, First I simply the equation asked for and then I use small values that make for easy computations and comparisons. 1. (1) says that X - Y = 1/2. This is insuff. Consider X = 1, Y = 1/2 AND X = 0, and Y = -1/2 (2) tells you that the sign of X and Y are equal AND also that X's absolute value is greater than that of Y's. Together, we find that X must be greater/equal to 1 since it is the only way to yeild a positive value given that X's absolute value is greater than Y.

The solution is more simple than one might think. You are correct: ab != 0 means that both a and b are not equal to 0. This information lets you evaluate the problem, ignoring this possibiliy. In over to solve DS questions I find it helpful to setup an equation or at least know what I'm looking for, in that way I can deduce whether it is sufficient from the additional information provided. In this case, if (-a,b) and (b,-a) are in the same quandrant then a and b HAVE THE SAME SIGN. This is what you need to discover, then the problem becomes simple: You need to discover two things in order to produce a "YES" response to this question: 1. Whether x and y have the same sign 2. If so, whether x (or y) share the same sign as either a or b. (1) Tells us that xy > 0, thus x and y are either both +ve or both -ve. This satifies 1. above, but is not sufficient, since 2. remains (2) Tells us that a and x have the same sign. This satisfies 2. above, but not 1. Thus, it is also insuffiecent alone. Taken together, (1) and (2) provide 1. and 2., respectively, and thus the answer to the probelm is C.

Agree with Chatru's approach

The number 75 can be written as the sum of the squares of 3 different positive integers. What is the sum of these 3 integers? A. 17 B. 16 C. 15 D. 14 E. 13 Given a sufficient amount of time, one can simply play with the arrangements of the perfect squares to eventually find that: are the numbers that provide the solution. However, I am looking for a mathematical (FASTEST) approach. Does anyone have any solutions or is trial-and-error the best we have to offer to this problem?

The smaller wheel must turn faster than the larger wheel in order for the the wheels to maintain the same distance. Let M = multiplier that the smaller wheel must turn in order to keep up with the larger wheel. (measure the distance the wheels "rotates" by their differences) M28pi = 35pi M = 5/4 So, the smaller wheel must move 5/4 as fast as the larger wheel, or the larger wheel moves 4/5 as fast as the smaller wheel. If the smaller wheel makes x rotations per second, then it makes 60x rotations per minute, then the larger wheel makes (4/5)60x rotations per minute 48x. Ans C.

The OA is E. The source is Manhattan GMAT. However, I also agree that the OA should be B. I have found that Manhattan is a great company for learning GMAT principles, but it falls short in the CR realm. By this, I mean that their CR questions do not closely resemble those of the OG.

Please provide your fastest solution and an explination. Thanks!

Hey tamGmat, I know the source of the question and the correct OA. I'd just like to say, that despite the source's reputation for other areas of the GMAT I have found that their CR questions are NOT strongly correlated with the real GMAT questions. So, just take questions from this source with a grain of salt when dealing with CR types.

Math education in this country does a disservice to our children. In the lower grades, it should focus on the basic skills that students will need in higher grades to develop the ability to solve complex problems. Learning basic math skills is like learning the scales and chords that one will later use to master complicated concertos and symphonies. However, math educators in this country seem to have it backward, emphasizing in higher grades the same narrow, skills-based approach that students learned in lower grades rather than the analytical tools they will need to solve complex math problems. Which of the following, if true, would most seriously weaken the conclusion drawn above? -While music is common in elementary school curriculums, it is rarely taught in high school. -On international tests of math skills, high-school students in this country performed no worse than did their counterparts from countries where problem-solving is emphasized in higher grades. -When presented with a math problem to solve, students in higher grades are more likely to arrive at different answers than students in lowers grades are. -Older students tend to receive higher grades in math than do younger students. -Universities in this country report a steady increase in the percentage of native first-year students who qualify to take advanced mathematics courses such as calculus.

Ans is A. The argument states that the government is not guillty of being fiscally wasteful. In order to achieve this the government must choose the cheapest means necessary in order to provide for its facilities. If new construction is cheaper than rehabing, then the government is taking the least expensive route. If this is not true, then the govornment is in fact being fically wasteful and thus the arugment would fall apart.

The ans is A. The argument states that the mechanics who do the first-time-around repair jobs are not incompetent, but just simply takes a second mechanic to correctly complete the job. "A" must be true, because if it was not it would mean that the the first-time-around mechanics are in fact incompetent and the second-time-around mechanics are sent out merely to fix the first-time-around mechanics' mistakes. Thus, the argument assumes A.