GMAT (Fach) / Economist Prep - IR (Lektion)
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- Skills needed Basic arithmetic (e.g., fractions, ratios, percentages—the usual stuff) Data reading and estimation (e.g., ballparking!) Data interpretation (i.e., the same sort of interpretation you already do for all problem-solving questions) Reading graphs and charts (A piece of cake compared to coordinate geometry, right?) Information analysis (i.e., analyzing information presented to you)
- Question Typen in IR Table Analysis (questions about a data table)Graphics Interpretation (questions about graphs or charts)Two Part Analysis (questions that have two-part answers)Multi-Source Analysis (questions about information you find in different information sources).
- Application questions 1. The author is most likely to agree with which of the following statements about (something that was mentioned in the passage)? 2. (Something that was mentioned in the passage) is most similar to which of the following? 3. Which of the following statements would provide the most logical continuation of the final paragraph of the passage? 4. Which of the following, if true, would best support the author's theory regarding (something that was mentioned in the passage)? specific Inferred
- Velocity SPEED TIME DISTANCE Speed (or velocity) is the rate of movement. It tells us what distance is covered in a time unit. It always carries units of length per time. For example: 0.3 centimeters per second, or 200 miles per hour.
- Average Speed Ballpark The average speed should be closer to the speed we spend more time in. Understanding and remembering this concept not only allows you to quickly choose B without calculating anything, but also helps you avoid the obvious trap answer C. Remember: average speed is not necessarily the average of the speeds.
- Average Speed - Handle a lot of data Let's summarize: Use the table to organize! 1. Fill the table: Assign each of the values in the question to the appropriate cell in the table. Use a new row whenever there is more than one journey, more than one traveler or more than one segment. 2. Highlight the value you are asked about 3. Plug in the answer choices until one of them fits in with all the data in the table.
- Speed Gap Problems The problem with the problem above, is that there are two moving objects, and two speeds. Time it takes to close the gap between Fanny and Alexander. The trick is to treat this gap as Work in a rate problem. The Work is the gap of 240 km. The Rate is the rate of closing the gap. "How does the gap change during one hour?" When a Speed Problem involves two moving objects and two speeds, concentrate on the gap between the two objects. Draw a sketch to help find the gap between the two objects. Find the rate of closing (or opening) of the gap. Ask yourself "How does the gap change every hour (or second, etc.)?" Turn the original problem into a Rate Problem where the gap is the Work, and the rate of closing/opening of the gap, is the Rate. Use the rate Box to organize the new information and find the required data.
- Carl and Mark run in opposite directions around a stadium. Carl runs at a constant speed, and so does Mark. Carl's speed is how many times greater than Mark's speed? (1) Mark completes a whole round every 60 seconds. (2) Carl and Mark meet every 24 seconds. Stat. (1): That's nice to know, but tells you nothing about Carl's speed. Stat.(1)->IS->BCE. Stat. (2) tells you that Mark and Carl take 24 seconds to cover the entire circuit of the stadium at their combined rate - Carl from his end, Mark from his. Think of the problem in terms of stadium parts/sec: they could each cover half a stadium in those 24 seconds, and then their speeds would be equal. But stat. (2) still allows other cases: for example, If mark covers a quarter of a stadium and Carl covers the remaining 3/4 in the same time, their speed ratio would be quite different. Alone, Stat.(2)->IS->CE. Stat. (1+2): draw a figure to help you see what's going on. Mark completes a full stadium in 60 seconds. Thus, in 24 seconds he completes 24/60 = 2/5 of the stadium. Stat. (2) tells you that together Mark and Carl complete a full stadium in those 24 seconds, thus Carl has to complete the remaining 3/5 of the stadium in 24 seconds. Since you now have both Carl's and Mark's rates, in terms in Stadium part/sec, it is possible to find the ratio between the two. Stat.(1+2)->S->C.
- Adding Workers The question usually starts with a hypothetical situation used to calculate the rate of each worker alone. Calculate in stages: Whenever the number of workers change - start a new stage. For every stage find the time to complete the stage and the work done in it.
- The mode The mode is another one of several terms you need to know in regard to a set of data. It means the number that appears the most in a set.
- Standard deviation Standard deviation is a simple measure of the variability or dispersion of a data set. A low standard deviation indicates that all of the data points are very close to the same value (the mean) A high standard deviation indicates that the data are “spread out” over a large range of values. The standard deviation is the square root of the average of the squares of the deviation of each member of the set from the mean.