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Math Revolution GMAT Instructor V
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Question Stats: 64% (01:55) correct 36% (02:03) wrong based on 199 sessions

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It’s well known that a company's profit=20,000x-25x^2, where x is the number of workers. If the profit of the company is the greatest, what is the value of x?

A. 50
B. 100
C. 150
D. 250
E. 400

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Originally posted by MathRevolution on 12 Oct 2016, 03:31.
Last edited by Bunuel on 12 Oct 2016, 03:58, edited 1 time in total.
Renamed the topic and edited the question.
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Re: It’s well known that a company's profit=20,000x-25x^2, where x is the  [#permalink]

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MathRevolution wrote:
It’s well known that a company's profit=20,000x-25x^2, where x is the number of workers. If the profit of the company is the greatest, what is the value of x?

A. 50
B. 100
C. 150
D. 250
E. 400

Notice the given formula P = 20,000x - 25x^2 is a quadratic function. Furthermore, the graph of this function will be a parabola opening downward, and the vertex of this parabola will be the maximum point of the graph. Since we need to determine a value of x in which the company makes the greatest profit, we need to determine the value of x at the vertex of the parabola.

Recall that x = -b/(2a) is the formula to find the x-value of the vertex; therefore, the number of workers that maximizes the profit is:

x = -20,000/[2(-25)] = -20,000/-50 = 400

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It’s well known that a company's profit=20,000x-25x^2, where x is the  [#permalink]

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Alternate approach:

To find Max or Min of a polynomial f(x), Equate f'(x)=0

f(x) = 20,000x-25x^2

Differentiate f(x)

f'(x) = 20,000 - 25*2*x = 0

50x = 20,000

x=400

D

Note: To confirm whether x is maximum or minimum, substitute x in f''(x)

If f''(x) <0, then f(x) is maximum

If f''(x) >0, then f(x) is minimum

In this case, f''(x)= -50 < 0
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Re: ) It’s well known that a company's profit=20,000x-25x^2, where  [#permalink]

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MathRevolution wrote:
It’s well known that a company's profit=20,000x-25x^2, where x is the number of workers. If the profit of the company is the greatest, what is the value of x?

A. 50 B. 100 C. 150 D. 250 E. 400

E - Used plugin after plotting a graph of this equation.
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Re: It’s well known that a company's profit=20,000x-25x^2, where x is the  [#permalink]

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MathRevolution wrote:
It’s well known that a company's profit=20,000x-25x^2, where x is the number of workers. If the profit of the company is the greatest, what is the value of x?

A. 50
B. 100
C. 150
D. 250
E. 400

So, $$Profit = 20000x - 25x^2$$

Or, $$Profit = x ( 20000 - 25x )$$

Quote:
Where x is the number of workers. If the profit of the company is the greatest, what is the value of x?

Now, to maximize profit we must minimize : ( 20000 - 25x )

Among the given options only (E) is the highest value for x , that can maximize the Final Value (Profit )

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Math Revolution GMAT Instructor V
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It’s well known that a company's profit=20,000x-25x^2, where x is the  [#permalink]

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It’s well known that a company's profit=20,000x-25x^2, where x is the number of workers. If the profit of the company is the greatest, what is the value of x?

A. 50 B. 100 C. 150 D. 250 E. 400
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Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 7472
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: It’s well known that a company's profit=20,000x-25x^2, where x is the  [#permalink]

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==>In general, from y=ax2+bx+c, the value of y from symmetric axis, x=-b/2a is the least or the greatest. For the profit has to be the greatest, x=-20,000/2(-25) = 400, hence the greatest profit. The answer is E.
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Re: It’s well known that a company's profit=20,000x-25x^2, where x is the  [#permalink]

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Abhishek009 wrote:
MathRevolution wrote:
It’s well known that a company's profit=20,000x-25x^2, where x is the number of workers. If the profit of the company is the greatest, what is the value of x?

A. 50
B. 100
C. 150
D. 250
E. 400

So, $$Profit = 20000x - 25x^2$$

Or, $$Profit = x ( 20000 - 25x )$$

Quote:
Where x is the number of workers. If the profit of the company is the greatest, what is the value of x?

Now, to maximize profit we must minimize : ( 20000 - 25x )

Among the given options only (E) is the highest value for x , that can maximize the Final Value (Profit )

Hi,
Sorry, slightly unclear on the highlivhted portion above, but should we not try to maximise the highlighted portion as bigger the multiple of x, higher the value of the profit. Please can anyone let me know what am i missing here.

Thanks
Manager  B
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Re: It’s well known that a company's profit=20,000x-25x^2, where x is the  [#permalink]

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Noted, thanks for the clarification!
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Re: It’s well known that a company's profit=20,000x-25x^2, where x is the  [#permalink]

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_________________ Re: It’s well known that a company's profit=20,000x-25x^2, where x is the   [#permalink] 20 Apr 2019, 22:57
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