GMAT Math : GMAT Quantitative Reasoning

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #2 : Range

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

\(\displaystyle \left.\begin{matrix} 4\\ 5\\ 6\\ 7\\ 8 \end{matrix}\right|\begin{matrix} \textrm{2 5}\; \; \; \; \; \; \; \; \; \; \;\; \; \; \; \; \; \; \; \; \;\\ \textrm{4 4 7 7}\; \; \; \; \; \; \; \; \; \; \;\; \; \; \; \\ \textrm{0 1 2 2 4 5 8 8 9}\\ \textrm{3 5 5 8} \; \; \; \; \; \; \; \;\; \; \; \; \; \; \; \\ \textrm{7 }\; \; \; \; \; \; \; \; \; \;\; \; \; \; \; \; \; \; \; \; \; \; \; \end{matrix}\)

What is the interquartile range of these test scores?

Possible Answers:

\(\displaystyle 16\)

\(\displaystyle 14\)

\(\displaystyle 9\)

\(\displaystyle 19\)

\(\displaystyle 12\)

Correct answer:

\(\displaystyle 14\)

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 interquartile range is the difference of the third and first quartiles.

The third quartile is the median of the upper half, or the upper ten scores. This is the arithmetic mean of the fifth- and sixth-highest scores. These scores are 73 and 69, so the mean is \(\displaystyle \left (73 +69 \right )\div 2 = 71\)

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.

The interquartile range is therefore the difference of these numbers: \(\displaystyle 71-57 = 14\)

Example Question #1 : Calculating Range

Consider the data set \(\displaystyle \left \{ 1, -2, 3, -4, 5, -6, 7, -8, 9, -10 \right \}\).

What is its midrange?

Possible Answers:

\(\displaystyle -4.5\)

\(\displaystyle 0\)

\(\displaystyle -1\)

\(\displaystyle -0.5\)

\(\displaystyle -5.5\)

Correct answer:

\(\displaystyle -0.5\)

Explanation:

The midrange of a data set is the arithmetic mean of its greatest element and least element. Here, those elements are \(\displaystyle 9\) and \(\displaystyle -10\), so we can find the midrange as follows:

\(\displaystyle \left [9 + (-10) \right ]\div 2 = -1\div 2 = -0.5\)

Example Question #3 : Descriptive Statistics

Set 1: 5, 13, -2, -1, 19, 27

Set 2: 6, -3, 23, 15, m, 1

What should the value of \(\displaystyle m\) be if we want the ranges of both sets of number to be equal?

Possible Answers:

\(\displaystyle -4\)

\(\displaystyle 25\)

\(\displaystyle -2\)

\(\displaystyle 30\)

\(\displaystyle -6\)

Correct answer:

\(\displaystyle -6\)

Explanation:

The range of a set of numbers is the difference between the highest number and the lowest number in the set.

The range of set 1 is:

 \(\displaystyle 27-(-2)=29\)

The range of the second set, ignoring the value of m is: 

\(\displaystyle 23-(-3)=26\)

We need to either subtract 3 from the lowest number in set Set 2 or add 3 to the highest number in Set 2 to get the value of m such that the range of both sets are equal.

\(\displaystyle m=(-3)-3=-6 \rightarrow range =23-(-6)=29\) 

or

\(\displaystyle m=23+3=26 \rightarrow range = 26-(-3)=29\) 

Example Question #4 : Calculating Range

Calculate the range of the following set of data:

\(\displaystyle (12, 15, 22, 24, 17, 9, 27, 21, 16, 23, 14)\)

Possible Answers:

\(\displaystyle 16\)

\(\displaystyle 18\)

\(\displaystyle 22\)

\(\displaystyle 21\)

\(\displaystyle 17\)

Correct answer:

\(\displaystyle 18\)

Explanation:

The range of a set of data is the difference between its highest value and its lowest value, as this describes the range of values spanned by the set. A quick way to calculate the range is to locate the lowest value in the set and subtract it from the highest value, but let's arrange the set in increasing order to visualize the problem first:

\(\displaystyle (9, 12, 14, 15, 16, 17, 21, 22, 23, 24, 27)\)

Now we can see that the lowest value in the set is 9, and the highest value in the set is 27, so the range of the set is:

\(\displaystyle 27 - 9 = 18\)

Example Question #1 : Descriptive Statistics

Calculate the range of the following set of data:

\(\displaystyle \begin{Bmatrix} 41, 28, 37, 41, 29, 33, 31, 40, 53, 49, 38, 42 \end{Bmatrix}\)

Possible Answers:

\(\displaystyle 28\)

\(\displaystyle 53\)

\(\displaystyle 49\)

\(\displaystyle 42\)

\(\displaystyle 25\)

Correct answer:

\(\displaystyle 25\)

Explanation:

The range of a set of data is the difference between its smallest and greatest values. We can first look through the set for the greatest value, which we can see is 53. We then look through the set for the smallest value, which we can see is 28. The range of the set is then:

\(\displaystyle 53-28=25\)

Example Question #2 : Calculating Range

Determine the mean for the following set of numbers.

\(\displaystyle {6,2,5,5,8,4}\)

Possible Answers:

\(\displaystyle 6\)

\(\displaystyle 2\)

\(\displaystyle 8\)

\(\displaystyle 5\)

\(\displaystyle 4\)

Correct answer:

\(\displaystyle 6\)

Explanation:

To find the range, simply subract the smallest number from the largest. Therefore:

\(\displaystyle 8-2=6\)

Example Question #2011 : Problem Solving Questions

Find the range of the following set of numbers:

\(\displaystyle \textup{4,6,7,7,8,10,28}\)

Possible Answers:

\(\displaystyle 10\)

\(\displaystyle 24\)

\(\displaystyle 8\)

\(\displaystyle 7\)

Correct answer:

\(\displaystyle 24\)

Explanation:

To find range, subtract the smallest number from the largest number. Thus,

\(\displaystyle \textup{range}=28-4=24\)

Example Question #2012 : Problem Solving Questions

Find the range of the following set of numbers.

1,1,2,7,8,10,11

Possible Answers:

\(\displaystyle 8\)

\(\displaystyle 1\)

\(\displaystyle 10\)

\(\displaystyle 7\)

Correct answer:

\(\displaystyle 10\)

Explanation:

To find the range, you m ust subtract the smallest number from the largest. Thus,

\(\displaystyle 11-1=10\)

Example Question #2011 : Gmat Quantitative Reasoning

Find the range of the following data set:

\(\displaystyle 89,34,117,42,367,2,989,463,865\)

Possible Answers:

\(\displaystyle 2\)

\(\displaystyle 444.5\)

\(\displaystyle 987\)

\(\displaystyle 989\)

Correct answer:

\(\displaystyle 987\)

Explanation:

Find the range of the following data set:

\(\displaystyle 89,34,117,42,367,2,989,463,865\)

Range is as simple as finding the diffference between the largest and smallest terms in a set. So, let's find our largest and smallest terms.

Largest: 989

Smallest: 2

Next, let's calculate the range:

\(\displaystyle r=989-2=987\)

So our answer should be 987

Example Question #14 : Descriptive Statistics

\(\displaystyle A = B > C > D = E > F\).

Give the midrange of the set \(\displaystyle \left \{ A, B, C, D, E,F\right \}\).

Possible Answers:

\(\displaystyle \frac{A+F}{2}\)

\(\displaystyle \frac{A +B+ C+D+E+F }{6}\)

\(\displaystyle C\)

\(\displaystyle \frac{C+D}{2}\)

\(\displaystyle D\)

Correct answer:

\(\displaystyle \frac{A+F}{2}\)

Explanation:

The midrange of a set is the arithmetic mean of the greatest and least values, which here are \(\displaystyle A\) and \(\displaystyle F\). This makes the midrange \(\displaystyle \frac{A+F}{2}\).

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