GMAT Math : Linear Equations, Two Unknowns

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #11 : Linear Equations, Two Unknowns

A toy store sells dolls for  dollars each and trucks for  dollars each. How many dolls did the store sell last week?

(1) Last week, the store sold twice as many trucks as dolls.

(2) Last week, the store made , dollars from selling trucks and dolls.

Possible Answers:

C: BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient

E: Statements (1) and (2) TOGETHER are not sufficient

D: EACH statement ALONE is sufficient

 

B: Statement (2) ALONE is sufficient, but statement (1) ALONE is not sufficient

A: Statement (1) ALONE is sufficient, but statement (2) ALONE is not sufficient

 

Correct answer:

C: BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient

Explanation:

Let:

t: the number of trucks sold last week

d: the number of dolls sold last week - d is the value we are looking to find

To evaluate the statements, we translate the word problems into equations

(1):  or 

(2): 

Each statement provides a single equation with two unknowns which is unsolvable, so each statement alone is not enough.

The two statements taken together give us a system of two equations with two unknowns, which we can solve.

Therefore the right answer is C.

 

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