GMAT Math : GMAT Quantitative Reasoning

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #13 : Understanding Absolute Value

Define an operation  as follows:

For all real numbers ,

Evaluate: 

Possible Answers:

Correct answer:

Explanation:

Example Question #12 : Absolute Value

Define an operation  as follows:

For all real numbers ,

Evaluate 

Possible Answers:

Correct answer:

Explanation:

Example Question #445 : Algebra

Define an operation  as follows:

For all real numbers ,

Evaluate 

Possible Answers:

Correct answer:

Explanation:

Example Question #14 : Understanding Absolute Value

Define a function  to be

Give the range of the function.

Possible Answers:

Correct answer:

Explanation:

An absolute value of a number must always assume a nonnegative value, so

, and

Therefore, 

and the range of  is the set .

Example Question #12 : Absolute Value

Solve the following equation:

Possible Answers:

Correct answer:

Explanation:

Before we apply the absolute value to the two terms in the equation, we simplify what's inside of them first:

Now we can apply the absolute value to each term. Remember that taking the absolute value of a quantity results in solely its value, regardless of what its sign was before the absolute value was taken. This means that that absolute value of a number is always positive:

Example Question #12 : Absolute Value

Give the range of the function

Possible Answers:

Correct answer:

Explanation:

The key to answering this question is to note that this equation can be rewritten in piecewise fashion. 

If , since both  and  are nonnegative, we can rewrite  as

, or

.

On  , this has as its graph a line with positive slope, so it is an increasing function. The range of this part of the function is , or, since

.

 

If , since  is negative and  is positive, we can rewrite  as

, or

 is a constant function on this interval and its range is .

 

If , since both  and  are nonpositive, we can rewrite  as

, or

.

On  , this has as its graph a line with negative slope, so it is a decreasing function. The range of this part of the function is , or, since 

.

 

The union of the ranges is the range of the function - .

Example Question #12 : Absolute Value

Give the range of the function

Possible Answers:

None of the other choices gives a correct answer.

Correct answer:

None of the other choices gives a correct answer.

Explanation:

The key to answering this question is to note that this equation can be rewritten in piecewise fashion. 

 

If , since both  and  are positive, we can rewrite  as

, or

,

a constant function with range .

 

If , since  is negative and  is positive, we can rewrite  as

, or

This is decreasing, as its graph is a line with negative slope. The range is ,

or, since

and

,

.

 

If , since both  and  are negative, we can rewrite  as

, or

,

a constant function with range .

 

The union of the ranges is the range of the function -  - which is not among the choices.

Example Question #21 : Understanding Absolute Value

Simplify the following expression:

Possible Answers:

Correct answer:

Explanation:

This question plays a few tricks dealing with absolute values. To begin, we can recognize that any negative sign within an absolute value can basically be rendered positive. So this:

becomes:

In this case, we still have a negative that was outside of the absolute value sign. This term will stay negative, so we get:

 

This makes our answer .

 

Example Question #21 : Absolute Value

Solve the following inequality:

Possible Answers:

Correct answer:

Explanation:

To solve this absolute value inequality, we must remember that the absolute value of a function that is less than a certain number must be greater than the negative of that number. Using this knowledge, we write the inequality as follows, and then perform some algebra to solve for :

Example Question #22 : Understanding Absolute Value

Solve the following inequality:

Possible Answers:

   or    

   or   

   or   

Correct answer:

   or    

Explanation:

To solve this absolute value inequality, we must remember that the absolute value of a function that is greater than a certain number is also less than the negative of that number. With this in mind, we rewrite the inequality as follows and then solve for the possible intervals of :

   or   

   or   

   or   

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