GMAT Math : GMAT Quantitative Reasoning

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #1561 : Gmat Quantitative Reasoning

A six-sided die is rolled, and a coin is flipped. If the coin comes up heads, the roll is considered to be the number that appears face up on the die; if the coin comes up tails, the outcome is considered to be half that number, with any fraction simply thrown out. What is the sample space of the experiment?

Possible Answers:

Correct answer:

Explanation:

If heads comes up on the coin, the number on the die is recorded. This can be any element of the set .

If tails comes up on the coin, half the number on the die is recorded, and any fraction is thrown out. Half the elements of the set  comprise the set  , but since we are throwing out the fractional parts, this becomes the set 

The sample space is the union of these two sets, which is .

Example Question #5 : Arithmetic

Temperature

Refer to the above graph, which shows the peak temperature in Smithville for each of seven days in a one-week period.

Between which two consecutuve days did the peak temperature see its greatest decrease?

Possible Answers:

Wednesday to Thursday

Friday to Saturday

Thursday to Friday

Tuesday to Wednesday

Monday to Tuesday

Correct answer:

Friday to Saturday

Explanation:

You only need to look for the portion of the line with the greatest negative slope, which is that which represents Friday to Saturday.

Example Question #11 : Arithmetic

Sets

The above represents a Venn diagram. The universal set  is the set of all positive integers.

Let  be the set of all multiples of 5; let  be the set of all perfect squares; let  be the set of perfect cubes. 

As you can see, the three sets divide the universal set into eight regions. Suppose each positive integer was placed in the correct region. Which of the following numbers would be in the same region as 1,225? 

Possible Answers:

Correct answer:

Explanation:

1,225 is divisible by 5 (last digit is 5). It is a perfect square, since . It is not a perfect cube, however, since .

Therefore, 1,225 is an element in  and , but not . We are looking for an element in  and , but not  - that is, a multiple of 5 and a perfect square but not a perfect cube.

By looking at the last digits, we can immediately eliminate 1,764 and 4,356, since neither is a multiple of 5. We can eliminate 15,625, since it s a perfect cube - 

Of the two remaining numbers, 3,375 is not a perfect square, since

3,025 is a perfect square: 

3,025 is not a perfect cube: 

3,025 is a multiple of 5, as can be seen from the last digit.

This is the correct choice.

Example Question #12 : Sets

Sets

The above represents a Venn diagram. The universal set  is the set of all positive integers.

Let  be the set of all multiples of 3; let  be the set of all multiples of 5; let  be the set of all multiples of 7.

As you can see, the three sets divide the universal set into eight regions. Suppose each positive integer was placed in the correct region. Which of the following numbers would be in the same region as 728?

Possible Answers:

Correct answer:

Explanation:

728 is divisible by 7, but not 3 or 5; therefore, 728 is in  but not  or . To be in the same region, a number must also be in  but not  or  - that is, divisible by 7 but not 3 or 5.

510 and 595 can be eliminated as multiples of 5 (from the last digit); 777 can be eliminated as a multiple of 3 (digit sum is 21). 

Now let's look at the two reminaing choices.

736 is not divisible by 7, since .

476 is not divisible by 3 or 5, but it is divisible by 7:

476 is the correct choice.

Example Question #12 : Arithmetic

Let  be the set , and  be the set .

 

What are the elements in the set   ?

Possible Answers:

Correct answer:

Explanation:

 is the set of all elements that are in both  and . So in this case the elements that are the same for both sets are , Note that the order that you present the elements in your set doesn't matter. What matters is that you don't exclude any necessary elements, or add any that don't belong.

Example Question #1561 : Problem Solving Questions

If  is the set of the multiples of  between  and  and  is the set of multiples of  between  and ; what is   ?

Possible Answers:

Correct answer:

Explanation:

So the intersection of A and B is the numbers that are in both A and B.

Thus 

Example Question #11 : Sets

Number_sets

Examine the above diagram, which shows a Venn diagram representing the sets of real numbers. 

If real number  were to be placed in its correct region in the diagram, which one would it be - I, II, III, IV, or V?

Statement 1:  is negative.

Statement 2: 

Possible Answers:

BOTH statements TOGETHER are insufficient to answer the question. 

EITHER statement ALONE is sufficient 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.

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 insufficient to answer the question. 

Explanation:

If both statements are assumed, then  - that is,  .   could fall in Region IV or V, as is shown in these two examples:

Example 1: 

, and  is rational, so  would be in Region IV.

Example 2: 

, and  is irrational, so  would be in Region V.

The two statements together are insufficient.

Example Question #11 : Arithmetic

Number_sets

Examine the above diagram, which shows a Venn diagram representing the sets of real numbers. 

 and  are both numbers in Region II, and they may or may not be equal. In how many of the five regions could the number  possibly fall?

Possible Answers:

One

Two

Five

Four

Three

Correct answer:

One

Explanation:

Region II comprises the whole numbers that are not natural numbers; however, there is only one such number, which is 0. Since  and  are both numbers in Region II, , forcing  to be in Region II.

Example Question #14 : Sets

Number_sets

Examine the above diagram, which shows a Venn diagram representing the sets of real numbers. 

 is a number in Region I, and  is a number in Region V. In how many of the five regions could the number  possibly fall?

Possible Answers:

Two

Three

Five

One

Four

Correct answer:

One

Explanation:

The key to answering this question is to know that the difference of any two rational numbers is also a rational number. 

Suppose  is rational. Since , being a natural number, is also rational, the difference 

must be rational.

But it is given that  is in Region V, making it irrational. This produces a contradiction. Therefore,  must be irrational, and it can only be in one region, Region V.

Example Question #11 : Sets

What is the fewest number of elements that a set can have in order to have more than 100 subsets?

Possible Answers:

Correct answer:

Explanation:

A set with  elements has exactly  subsets. 

, so a set with 6 elements has 64 subsets.

, so a set with 7 elements has 128 subsets.

The correct response is 7.

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