GMAT Math : Arithmetic

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #13 : Descriptive Statistics

A data set comprises 1,000 entries. What is its interquartile range?

Statement 1: The 75th percentile is 64.

Statement 2: The 25th percentile is 30.

Possible Answers:

BOTH statements TOGETHER are insufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

EITHER statement ALONE is sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Explanation:

The interquartile range is the difference between the third and first quartiles - that is, the 75th percentile and the 25th percentile. Knowing both is necessary and sufficient.

Example Question #182 : Arithmetic

Seven kids in a kindergarten class have the following ages:

.

Amy and Lilly join this kindergarten class. What is the range of the nine kids' ages?

(1) Amy is  years old.

(2) The sum of the ages of both kids is .

Possible Answers:

BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient

Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient

Statements (1) and (2) TOGETHER are not sufficient

Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient

EACH statement ALONE is sufficient

Correct answer:

BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient

Explanation:

Statement (1) alone does not give us any information to find out the age of Lilly, therefore it is not sufficient.

Statement (2) alone does not give us enough information to determine the ages of each kid. Therefore it is not sufficient.

Statement (1) and (2) give us the following information:

A = 6 and A + L = 13, therefore L = 13 - 6 = 7

With the ages of both kids we can find the new age range = 8 - 2 = 6

Example Question #11 : Dsq: Calculating Range

What is the value of  in the list above?

(1) The range of the numbers in the list is .

(2) 

Possible Answers:

Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient.

Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

Both statements TOGETHER are not sufficient.

Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient.

Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient.

Correct answer:

Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient.

Explanation:

Statement (1) indicates that the range of the numbers is 20. The range is the difference between the highest number and the lowest number. The difference between each pair of numbers in the list is less than 20. Therefore, n is the lowest number in the list. We can then calculate n as follows:

Therefore Statement (1) is SUFFICIENT.

Statement (2) states that n<5 which means n is the lowest number in the list. However this information alone is not sufficient to find the value of n.

Therefore Statement (2) is not SUFFICIENT.

Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient.

 

 

Example Question #14 : Descriptive Statistics

What is the range of the numbers in the list above?

(1) .

(2) .

Possible Answers:

Statements (1) and (2) TOGETHER are not sufficient.

Both statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient.

Each Statement ALONE is sufficient.

Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient.

Correct answer:

Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient.

Explanation:

The range of a set of numbers is the difference between the maximum and the minimum values of these numbers. In order to determine the range of these numbers, we need to know the values of n and 2n-1 or at least we should know that n and 2n-1 are not the minimum or the maximum values, meaning n and 2n-1 do not affect the range of these numbers.

(1) 

Therefore n is not the minimum value in this list. However, we do not if 2n-1 is the maximum value. Statement (1) ALONE is not sufficient.

(2)

n and 2n-1 do not affect the range then. The range of these numbers is:

Statement (2) ALONE is sufficient.

Example Question #1 : Dsq: Calculating Arithmetic Mean

Is 3 the average of a sequence?

(1)There are 3 numbers in the sequence

(2)The mode of the sequence is 3

Possible Answers:

Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

EACH statement ALONE is sufficient.

BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

Statements (1) and (2) TOGETHER are NOT sufficient.

Correct answer:

Statements (1) and (2) TOGETHER are NOT sufficient.

Explanation:

For statement (1), since we don’t know the value of each number, we cannot calculate the average of the sequence. For statement (2), the mode of the sequence is 3 means that “3” occurs most times in the sequence, but we cannot get to the average because we don’t know the value of other numbers. If we look at the two conditions together, we will know that there are 2 or 3 “3”'s in the sequence, but we don’t know exactly how many times “3” occurs. If the 3 numbers are all “3”s, then we can answer the question; If not, then we cannot answer the question. Thus both statements together are not sufficient.

Example Question #2 : Dsq: Calculating Arithmetic Mean

Calculate the average of the 5 integers.

Statement 1: They are consecutive even integers.

Statement 2: The smallest of the integers is 8 less than the largest of the five integers.

Possible Answers:

EACH statement ALONE is sufficient.

Statement 1 ALONE is sufficient, but statement 2 is not sufficient.

BOTH statements TOGETHER are sufficient, but NIETHER statement ALONE is sufficient.

Statement 2 ALONE is sufficient, but statement 1 is not sufficient.

Statements 1 and 2 TOGETHER are NOT sufficient.

Correct answer:

Statements 1 and 2 TOGETHER are NOT sufficient.

Explanation:

We are looking for an average here. Statement 1 tells us we are looking for even consecutive integers such as 2, 4, 6, 8, and 10. Statement 2 tells us the difference between the smallest and largest integer; however, the difference between the largest and smallest of five consecutive even (or odd) integers will ALWAYS be 8, regardless of what 5 consecutive integers we choose; therefore the two statements don't give us enough information to solve for the average. 

Example Question #3 : Dsq: Calculating Arithmetic Mean

Data sufficiency question- do not actually solve the question

Find the mean of a set of 5 numbers.

1. The sum of the numbers is 72.

2. The median of the set is 15.

Possible Answers:

Both statements taken together are sufficient to answer the question, but neither question alone is sufficient

Statement 1 alone is sufficient, but statement 2 is not sufficient to answer the question

Each statement alone is sufficient

Statements 1 and 2 are not sufficient, and additional information is required to answer the question

Statement 2 alone is sufficient, but statement 1 is not sufficient to answer the question

Correct answer:

Statement 1 alone is sufficient, but statement 2 is not sufficient to answer the question

Explanation:

Statement 2 does not provide enough information about the mean as it can vary greatly from the median. Statement 1 is sufficient to calculate the mean, because even though it is impossible to calculate the set of numbers, the mean is calculated by dividing the sum by the total number of incidences in the set.

Example Question #4 : Dsq: Calculating Arithmetic Mean

How much greater is the average of the integers from 500 to 700 than the average of the integers from 60 to 90?

Possible Answers:

Correct answer:

Explanation:

In this case, average is also the middle value.

Example Question #5 : Dsq: Calculating Arithmetic Mean

What is the arithmetic mean of a data set with twenty data values, each of which is a positive integer?

1) The sum of the odd values is 1,144 and the sum of the even values is 856.

2) The sum of the lowest ten values is 400 and the sum of the greatest ten values is 1,600.

Possible Answers:

Statement 2 ALONE is sufficient, but Statement 1 alone is not sufficient.

BOTH statements TOGETHER are sufficient, but neither statement ALONE is sufficient.

Statements 1 and 2 TOGETHER are not sufficient.

EACH statement ALONE is sufficient.

Statement 1 ALONE is sufficient, but Statement 2 alone is not sufficient.

Correct answer:

EACH statement ALONE is sufficient.

Explanation:

The arithmetic mean of a data set is the sum of the values divided by the number of values in the set. Since we know that there are 20 values, all we need is the sum of the values. The sum can be easily deduced to be 2,000 from either one of the statements, so the arithmetic mean can be determined to be .

The answer is that either statement alone is sufficient.

Example Question #1173 : Data Sufficiency Questions

In western North Carolina, three towns lie along scenic rte 129 (the old Tallulah road). From north to south they are - Bear Creek, Sweet Gum and Robbinsville. Each town boasts of 6 establishments that sell moonshine (18 establishments total). Henry decides to test the alcohol content in all 18 establishemnts to see if there is a significant difference between the proof level in each town. He gathers the folloiwng evidence -

Robbinsville - 171, 170, 166, 180, 170, 177; avg=172.3; variance=26.67

Sweet Gum - 181, 177, 164, 190, 181, 180; avg = 178.8; variance=71.77

Bear Creek - 170, 180, 171, 191, 188, 188; avg=181.3; variance=83.87 

The null hypothesis is: the 3 averages are the same.

Use the ANOVA F-test to see if we can reject the null hypothesis at the 95% level of confidence. Give both the F value and the percentile value (p) for the test. 

Hint - ANOVA compares the variation between samples (MSB) to the variation within samples (MSW). If MSB is much greater than MSW, then we reject the null hypothesis and conclude that the 3 samples are significantly different. The F statistic is calculated MSB/MSW.  

Possible Answers:

F=3.68

p=0.05

F=4.6

p=0.02

F=4.1

p=0.04

F=2.81

p=0.10

F=2.13

p=0.15

Correct answer:

F=2.13

p=0.15

Explanation:

The number of sample for each town = 6; N=6; E = 6-1 = 5

Overall average (of all 18 establishments) = 177.5 = O

Number of towns (columns) = 3; V1=3-1=2

total samles = 18; V2=18-3 = 15

For an F value of 2.13 with V1=2 and V2 = 15, p = .153

So, we can not reject the null hypothesis because our data would occur 15% of the time assuming the 3 averages are equal.  

Note - the cutoff F value for 95% is 3.68

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