Mean

 Categories : Mean, Descriptive Statistics, Problem Solving Average Question is an important topic in GMAT problem solving and data sufficiency. Let us start with the Basics. Average (Arithmetic Mean) Average of n numbers a1, a2, a3, a4, a5....an (An) = (a1+a2+.....an) /nExample: Find the average of 34, 56, 75 and 83Answera1 = 34a2= 56a3=75a4 = 83Total Number of Elements (n) = 4 Average (An) = (a1+a2+a3+a4)/n= (34 + 56 + 75 + 83)/4 = 62Shortcut to Remember:  An x n = a1+a2+.......anLet us straight away apply this shortcutQ) The average of four numbers is 20. If one of the numbers is removed, the average of the remaining numbers is 15. What number was removed?(A) 10(B) 15(C) 30(D) 35(E) 45Answer: Four Numbers = a1, a2, a3, a4 n=4An = 20An x n = a1 + a2 + a3 + a4 20... Even if you fear statistics by its reputation, it is one of the easiest sections in the GMAT because a standard set of questions is asked and anyone who understands the fundamentals that I shall describe will be able to ace the questions. The three most basic topics in stats are mean, mode, and median. Usually, the GMAT will go one step further into range and standard deviation.Mean: Mean is the average. Let’s say there are two numbers: 6 and 8. The mean would be:(6+8)/2 =14/2 =7. If you analyze the number 7, it makes sense that it is average of 6 and 8. Using the same approach, the mean of n numbers a1,a2,a3…….an would be (a1+a2+a3…..+an)/n. If you remember this formula, you should be able to do well with mean questions. We shall discuss some of the standard questions in subsequent blogs, but for right now, remember the key formula and start doing some mean and average questions from Grockit games.Mode: Let’s say that you are given a set of numbers, such as {4,3,7,9,9,11,10}. In order to find the mode, you have to arrange the numbers in ascending...

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