### All GMAT Math Resources

## Example Questions

### Example Question #1 : Understanding Real Numbers

Solve for *x*.

**Possible Answers:**

**Correct answer:**

Add 3 to both sides:

Divide both sides by 2:

### Example Question #1 : Real Numbers

Of 200 students, 80 take biology, 40 take chemistry, 60 take physics, 13 take two science courses, and no one takes three science courses. How many students are not taking a science course?

**Possible Answers:**

**Correct answer:**

To calculate the number of students taking at least 1 science course, add the number of students who are taking each course and subtract the number of students who are taking 2 (to ensure they're not counting twice).

To calculate the number of students NOT taking a class, subtract this number by the total number of students.

### Example Question #1 : Real Numbers

Which of the following expressions is equal to

**Possible Answers:**

**Correct answer:**

### Example Question #1 : Real Numbers

Given that , , and , evaluate .

**Possible Answers:**

Not enough information is given to answer the question

**Correct answer:**

To find :

,

so

Since ,

and we choose the positive square root

### Example Question #1 : 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:**

**Correct answer:**

Today, . In 3 years, .

### Example Question #1 : Real Numbers

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

**Possible Answers:**

**Correct answer:**

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 #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:**

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:**

122

125

-3

-122

3

**Correct answer:**

3

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 #9 : 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:**

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 #3 : Number Theory

If are both negative, then could NOT be equal to....

**Possible Answers:**

**Correct answer:**

is negative and is positive

Therefore, the solution cannot be negative.

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