GMAT Math : Arithmetic

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #7 : Understanding Real Numbers

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 : Understanding Real Numbers

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

Possible Answers:

122

-122

-3

3

125

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 : Understanding 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:

Not enough information given.

Greater than

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 #2 : Real Numbers

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 5

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

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 #411 : Arithmetic

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 #412 : Arithmetic

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

Possible Answers:

Six hundred thirty-three ten-thousandths

Three hundred thirty-six ten-thousandths

Three hundred sixty-six ten-thousandths

Six hundred six ten-thousandths

Six hundred 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 #1961 : Gmat Quantitative Reasoning

Which of the following is equal to 0.0407?

Possible Answers:

Four hundred seven ten-thousandths

Four hundred seventy ten-thousandths

Four hundred seven one-thousandths

Forty-seven ten-thousandths

Four hundred seventy one-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.

Example Question #12 : Understanding Real Numbers

Which of the following is equal to three one-hundredths subtracted from one fourth?

Possible Answers:

Twenty-three one-hundredths

Thirty-seven one-hundredths

Five one-hundredths

Twenty-two one-hundredths

Forty-seven one-hundredths

Correct answer:

Twenty-two one-hundredths

Explanation:

The one-hundredths place is the second place to the right of the decimal point; therefore, three one-hundredths is equal to 0.03. One fourth can be converted to decimal form as follows:

,

which is twenty-five one-hundredths, or 0.25. Subtract:

,

or twenty-two one-hundredths.

Example Question #15 : Understanding Real Numbers

Order  from least to greatest.

Possible Answers:

Correct answer:

Explanation:

We can find each in terms of .

 

 

 

In ascending order, the numbers are:

 

The correct choice is  .

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