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Which of the following values of x gives the greatest value of y in

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Which of the following values of x gives the greatest value of y in  [#permalink]

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New post 09 Nov 2015, 00:08
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

88% (00:33) correct 12% (00:42) wrong based on 161 sessions

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Which of the following values of x gives the greatest value of y in  [#permalink]

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New post 09 Nov 2015, 02:25
(A) 200
y= 248 - 398*200
= big negative number
(B) 100
y= 248 - 398*100
=negative number but smaller than A
(C) 0.5
y= 248 - 398*.5
= 248 - 199
= 49
(D) 0
y=248

(E) -1
y=248 - (398*-1)
=248+398
=646

Answer E
y = 248 - 398x
Value of y will depend on both sign and absolute value of x .
As value of x increases , then values of y will decrease . Since , there is only one negative number x=-1 in the choices , value of y will be maximum for that .
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Re: Which of the following values of x gives the greatest value of y in  [#permalink]

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New post 09 Nov 2015, 07:07
Clearly, the negative value of x will result in maximum value of y.
Don't even look at the rest of the answer choices as only one negative value is being present.

Answer is E
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Re: Which of the following values of x gives the greatest value of y in  [#permalink]

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New post 29 Sep 2017, 10:29
Bunuel 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


We see that if x is negative, rather than subtracting 398x from 248, we are summing the values. 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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Re: Which of the following values of x gives the greatest value of y in &nbs [#permalink] 29 Sep 2017, 10:29
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