GMAT Math : GMAT Quantitative Reasoning

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #4 : Real Numbers

Today, Becky's age (B) is 3 times Charlie's age. In 3 years, what will Charlie's age be in terms of B?

Possible Answers:

\small \frac{B}{3}+3

\small 3(B+3)

\small 3B+3

\small \frac{B+3}{3}

\small 3(B+3)

\small 3B+3

Correct answer:

\small \frac{B}{3}+3

Explanation:

Today, \small C=\frac{B}{3}. In 3 years, \small C=\frac{B}{3}+3.

Example Question #1 : Real Numbers

Given that  and , what is the range of possible values for  ?

Possible Answers:

Correct answer:

Explanation:

The lowest possible value of  is the lowest possible value of  divided by the highest possible value of 

The highest possible value of  is the highest possible value of  divided by the lowest possible value of 

Example Question #411 : Arithmetic

If and  are composite integers, which of the following can be prime?

Possible Answers:

None of these can be prime.

Correct answer:

Explanation:

so this is a composite number for all  and .

is by definition a composite number.

the product of 2 numbers.

This leaves just .  For a number to be prime, it must be odd (except for 2) so we need to have either or be odd (but not both).  The first composite odd number is 9.  .  The smallest composite number is 4. .  

is a prime number.  

So the answer is

Example Question #1 : Real Numbers

If  is a real number, which of the following CANNOT be a value for x?

Possible Answers:

125

-122

-3

122

3

Correct answer:

3

Explanation:

The definition of the set of real numbers is the set of all numbers that can fit into a/b where a and b are both integers and b does not equal 0. 

So, since we see a fraction here, we know a non-real number occurs if the denominator is 0. Therefore we can find where the denominator is 0 by setting x-3 =0 and solving for x. In this case, x=3 would create a non-real number. Thus our answer is that x CANNOT be 3 for our expression to be a real number. 

Example Question #1 : Real Numbers

Let  be the product of integers from 18 to 33, inclusive. If , how many more unique prime factors does  have than ?

Possible Answers:

Greater than

Not enough information given.

Correct answer:

Explanation:

This question does not require any calculation. Given that 32 (an even number) is a factor of , then 2 must be a prime factor. If  is then multiplied by 2 (to get ) then  has no additional unique prime factors (its only additional prime factor, 2, is NOT unique).

Example Question #1962 : Problem Solving Questions

If \dpi{100} \small x\ and\ y are both negative, then \dpi{100} \small \frac{x+y}{-xy} could NOT be equal to.... 

 

Possible Answers:

\dpi{100} \small 5

\dpi{100} \small \frac{3}{4}

\dpi{100} \small \frac{\sqrt{8}}{4}

\dpi{100} \small -5

Correct answer:

\dpi{100} \small -5

Explanation:

\dpi{100} \small x+y is negative and \dpi{100} \small xy is positive

\dpi{100} \small \frac{Negative}{-Positive} = \frac{Negative}{Negative} = Positive

Therefore, the solution cannot be negative.

Example Question #2 : Real Numbers

If  is a real number, which one of these cannot be a value of ?

Possible Answers:

Correct answer:

Explanation:

For the expression to be defined, the denominator needs to be different from 0. Therefore:

So the correct answer is 2.

Example Question #1961 : Problem Solving Questions

If , and , and , what can we say for sure about ?

Possible Answers:

is positive

 is negative

None of the other answers.

Correct answer:

None of the other answers.

Explanation:

To show the other answers aren't always true, we need to choose 2 numbers that satisfy the given inequalities but also contradict each answer one-by-one.

 

Let this choice shows that sometimes , which rules out the answers is negative, and

 

Now Let , this will still satisfy the given inequalities, but now . This means that the answer " is positive" isn't always true either.

Example Question #11 : Understanding Real Numbers

Which of the following is equal to the sum of thirty-three one-thousandths and three hundred three ten-thousandths?

Possible Answers:

Three hundred sixty-six ten-thousandths

Six hundred three ten-thousandths

Three hundred thirty-six ten-thousandths

Six hundred six ten-thousandths

Six hundred thirty-three ten-thousandths

Correct answer:

Six hundred thirty-three ten-thousandths

Explanation:

The one-thousandths and ten-thousandths places are the third places and the fourth places, respectively, to the right of the decimal point. Therefore:

Thirty-three one-thousandths = 

Three hundred three ten-thousandths = 

Add:

The last nonzero digit ends at the ten-thousandths place, so this is , or 

 six hundred thirty-three ten-thousandths.

Example Question #12 : Understanding Real Numbers

Which of the following is equal to 0.0407?

Possible Answers:

Four hundred seventy one-thousandths

Four hundred seven ten-thousandths

Four hundred seven one-thousandths

Forty-seven ten-thousandths

Four hundred seventy ten-thousandths

Correct answer:

Four hundred seven ten-thousandths

Explanation:

The last nonzero digit is located in the fourth place right of the decimal point - the ten-thousandths place. Put the number, without decimal point or leading zeroes, over 10,000. This number is , or four hundred seven ten-thousandths.

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