GMAT Math : DSQ: Solving linear equations with one unknown

Study concepts, example questions & explanations for GMAT Math

varsity tutors app store varsity tutors android store

Example Questions

2 Next →

Example Question #11 : Linear Equations, One Unknown

. What is ?

(1) 

(2) 

Possible Answers:

Statement 2 alone is sufficient.

Statements 1 and 2 together are not sufficient.

Statement 1 alone is sufficient.

Both statements together are insufficient.

Each statement alone is sufficient.

Correct answer:

Each statement alone is sufficient.

Explanation:

Firstly, we should try to find a simplified equation to better see the possible values for . We get . We can see that  can either be  or .

Statement 1 tells us that the square of  is . It follows that  must be , therefore, this statement is sufficient.

Statement 2 tells us that the absolute value of  is , therefore  must be  and therefore the statement is also sufficient alone.

Note that it is possible to answer with either statement only because  can either be  or . If  could have been  or  than statements 1 and 2 would have been insufficient.

Example Question #931 : Data Sufficiency Questions

What is  if,  ?

(1) 

(2) 

Possible Answers:

Both statements together are sufficient.

Each statement alone is sufficient.

Statement 2 alone is sufficient.

Statement 1 alone is sufficient.

Statements 1 and 2 together are not sufficient.

Correct answer:

Both statements together are sufficient.

Explanation:

To begin with this problem, we should try to solve  . It gives us two sets of equations for us to find values for   and . Solving gives us two possible values for   and . Let's see how can the statements help us determine the value of  .

Statement 1 gives us an other unknown for the value of  . Therefore, this statement is insufficient.

Statement 2 gives an absolute value for this unknown . But we don't know what other values is  equal to.

Taken together these statements, allow us to see that   must be  and therefore are sufficient to answer the question.

Example Question #932 : Data Sufficiency Questions

. What is  ?

(1) 

(2) 

Possible Answers:

Statements 1 and 2 together are not sufficient.

Statement 1 alone is sufficient.

Each statement alone is sufficient.

Both statements together are sufficient.

Statement 2 alone is sufficient.

Correct answer:

Each statement alone is sufficient.

Explanation:

To approach this problem, we should firstly set up two possible equations for the value of  ; either  or 

Statement 1 tells us that  is in fact zero. Than the equations return a single value for  , therefore statement 1 alone is sufficient. 

Statement 2 tells us that , if plug in this value for , we get that:

Because there is the absolute value we get two equations:

 

or 

 must be 8. Plugging in the value for  in our first equation gives us no solution because both sides are of equal value and we end up with .

Therefore, statement 2 alone is sufficient

 

To conclude, each statement alone is sufficient.

Example Question #933 : Data Sufficiency Questions

What is ?

(1) 

(2) 

Possible Answers:

Statement 2 alone is sufficient.

Each statement alone is suffcient.

Both statements together are sufficient.

Statements 1 and 2 taken together are not sufficient.

Statement 1 alone is sufficient.

Correct answer:

Statements 1 and 2 taken together are not sufficient.

Explanation:

To answer this question, we must find a single value for .

Statement 1 gives us an equation with two possible solutions for . Therefore, statement 1 alone is not sufficient, since  can either be  or 

Statemnt 2 alone is also insufficient, because it gives us the same possible values for  as the equation in statement 1.

When two statements give us the same the information the answer is either both statements together are sufficient or statements 1 and 2 together are not sufficient. Here neither statement allowed us to answer, it follows that statements 1 and 2 together are not sufficient.

Example Question #934 : Data Sufficiency Questions

, What is ?

(1) 

(2) 

Possible Answers:

Statement 2 alone is sufficient.

Statements 1 and 2 together are not sufficient.

Both statements together are sufficient.

Statement 1 alone is sufficient.

Each statement alone is sufficient.

Correct answer:

Both statements together are sufficient.

Explanation:

To find a value for , we should be able to get a value for .

Statement 1 has two unknowns therefore we need another different equation with  to be able to find values for these unknowns.

Statement 2 alone is also insufficient because just as statement 1 has two variables and therefore we need more information to solve it.

Taking together these equations, by adding both sides we get   and from there we can find a single value for .

Both statements together are sufficient.

Example Question #935 : Data Sufficiency Questions

 and  is different than . What is ?

(1) 

(2)  is not an integer. 

 

Possible Answers:

Each statement alone is sufficient.

Both statements together are sufficient.

Statement 1 alone is sufficient.

Statement 2 alone is sufficient.

Statements 1 and 2 together are sufficient.

Correct answer:

Statement 1 alone is sufficient.

Explanation:

Firstly we should try to see what are the possible values for , by solving the equations given by the absolute value:

either   or  .

This allows us to find two values for  which are  and , let's see how the statements can help us determine a single value for .

Statement 1 tells us that  must be greater than one. Only one of our solutions for  is greater than one. Therefore, statement 1 alone is sufficient.

Statement 2 tells us that  is not an integer, however both solutions are not integer values and therefore statement 2 doesn't help us find a single solution.

Statement 1 alone is sufficient.

2 Next →

Tired of practice problems?

Try live online GMAT prep today.

1-on-1 Tutoring
Live Online Class
1-on-1 + Class
Learning Tools by Varsity Tutors