GMAT Math : GMAT Quantitative Reasoning

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #6 : Median

Consider the data set

For the median to be 70, what must be true about  and ?

Possible Answers:

One must be equal to 70; the other must be greater than or equal to 70.

One must be equal to 70; the other must be greater than 70.

One must be equal to 70; the other must be less than or equal to 70.

Both must be equal to 70.

One must be equal to 70; the other must be less than 70.

Correct answer:

One must be equal to 70; the other must be greater than or equal to 70.

Explanation:

There are nine elements, so the median is the fifth-highest element. For this fifth-highest element to be 70, first of all, 70 must be in the set; since none of the known elements are equal to 70, then one of the two unknowns must be 70.

Assume without loss of generality that . Then four of the elements are already known to be less than 70. Since four elements must be greater than or equal to 70,  must be one of them.

Therefore, the correct choice is that one must be equal to 70 and the other must be greater than or equal to 70.

Example Question #73 : Descriptive Statistics

What is the median of the following set:

Possible Answers:

Correct answer:

Explanation:


Put the numbers in order from least to greatest:

The middle number is the median.

Example Question #9 : Calculating Median

Below is the stem-and-leaf display of a set of test scores.

What is the median of these scores?

Possible Answers:

Correct answer:

Explanation:

The numbers in the "stem" of this display represent tens digits of the test scores, and the numbers in the "leaves" represent the units digits.

This stem-and-leaf display represents twenty scores, so the median is the arithmetic mean of the tenth- and eleventh-highest elements. These elements are 62 and 64, so the median is .

Example Question #1 : Median

Below is the stem-and-leaf display of a set of test scores.

What is the first quartile of these test scores?

Possible Answers:

Correct answer:

Explanation:

The numbers in the "stem" of this display represent tens digits of the test scores, and the numbers in the "leaves" represent the units digits.

This stem-and-leaf display represents twenty scores. The first quartile is the median of the lower half, or the lower ten scores. This is the arithmetic mean of the fifth- and sixth-lowest scores. Both of these scores are the same, however - 57. Therefore, 57 is the first quartile.

Example Question #71 : Descriptive Statistics

Consider the data set 

What is its median?

Possible Answers:

Correct answer:

Explanation:

Arrange the elements in ascending order:

There are ten elements, so the median is the arithmetic mean of the fifth- and sixth-highest elements, which are . This mean is 

Example Question #71 : Descriptive Statistics

Sally is collecting information about the lengths of tree branches that fell in her back yard during a powerful storm the night before. With her trusty measuring stick, she measures out 10 different branches and finds their lengths in feet to be

 

Calculate the median of the branch lengths

Possible Answers:

9.5

9

6.5

6.4

5

Correct answer:

6.5

Explanation:

In order to find the median, we first have to order the data points from lowest to highest. This would be-

 

.

 

Since we have an even number of data points, the median is the mean average of the middle two numbers, .

 

Hence our answer is 

Example Question #12 : Median

 employees of Company X are randomly selected. Given their ages listed below, what is the median age of the employees of Company X?

Possible Answers:

Correct answer:

Explanation:

We start by sorting the ages from youngest to oldest:

19  21  23  24  25  29  33  37  38  42  43  47  48  53  68

The median is the number in the middle position, we have fifteen numbers so the middle position in this set is the 8th position (we get 7 numbers on each side of the 8th number)

37 is at the 8th position, therefore 37 is the median age.

Example Question #12 : Calculating Median

What is the value of  if  is the difference between the range and the median of the numbers in the list?

Possible Answers:

Correct answer:

Explanation:

To find the median, let's rewrite the list in ascending order:

5, 5, 9, 10, 12, 14, 22, 27, 39

The median is the midpoint value such that half of the values are lower than the median and the other half of the values are higher than the median.

The median is 12.

The range is the difference between the highest and the lowest number in the list. The range is: 39-5=34

 

The difference between the range and the median is 22.

Example Question #2 : How To Find Median

67, 73, 85, 83, 80, 73, 94, 65, 80, 73, 98, 59, 76

The list above shows a ninth grader's grades for the academic year. What is the difference between the median and the mode of these grades?

Possible Answers:

Correct answer:

Explanation:

To find the median, sort the numbers from smallest to largest:

59, 65, 67, 73, 73, 73, 76, 80, 80, 83, 85, 94, 98

The median is the middle value in a list of numbers, it is the number separating the higher half of a data sample or a list of numbers from the lower half.

The median of the grades is 76.

The mode is the value occurring most often. The most occurring value in the list of numbers given is 73. So, the mode is 73.

Example Question #84 : Descriptive Statistics

Determine the median of the following set of data:

Possible Answers:

Correct answer:

Explanation:

The median of a set of data is the entry located exactly in the middle when the entries are arranged in increasing order. If there are an odd number of entries arranged in increasing order, the median will be the middle entry. If there are an even number of entries arranged in increasing order, the median will be the average of the middle two entries. Our first step, then, is to arrange the given set in increasing order:

    

Now that our set is in order from least to greatest, we can see that the value of 6 is located exactly in the middle of the set, so this is the median.

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