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y = 248 - 398x. Which of the following values of x gives

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y = 248 - 398x. Which of the following values of x gives

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$$y=248-398x$$ Which of the following values of x gives the greatest value of y in the equation above?

(A) 200
(B) 100
(C) 0.5
(D) 0
(E) -1

OA=E

Source: GMAT Prep

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VJesus12 wrote:
$$y=248-398x$$ Which of the following values of x gives the greatest value of y in the equation above?

(A) 200
(B) 100
(C) 0.5
(D) 0
(E) -1

OA=E

Source: GMAT Prep
We can also test the answer choices....

(A) x = 200 means y = 248 - 398(200) = some number LESS THAN 248
(B) x = 100 means y = 248 - 398(100) = some number LESS THAN 248
(C) x = 0.5 means y = 248 - 398(0.5) = some number LESS THAN 248
(D) x = 0 means y = 248 - 398(0) = some number EQUAL TO 248
(E) x = -1 means y = 248 - 398(-1) = 249 + 398 = some number GREATER THAN 248

Answer: E

Cheers,
Brent

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VJesus12 wrote:
$$y=248-398x$$ Which of the following values of x gives the greatest value of y in the equation above?

(A) 200
(B) 100
(C) 0.5
(D) 0
(E) -1

OA=E

Source: GMAT Prep
We see that if x is negative, rather than subtracting 398x from 248, we are summing the values of 248 and |398x|. Thus, when x is -1, we can get the largest value of y.

Alternate solution:

We see that the given equation is a line with a negative slope (i.e., a line that is going down from left to right). Thus, the smaller the x-value, the larger the y-value. Therefore, when x is the smallest, y will be the largest. The smallest x-value given is -1 and it will yield the maximum y-value.

Answer: E

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Scott Woodbury-Stewart
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scott@targettestprep.com



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