SOLUTION: sammy is selling widgets. If he sells 1 widget, it costs him $1 to produce it and he can sell it for $10. If he sells 2 widgets, it costs him $2 to produce 2 widgets, but he can on

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Question 1206524: sammy is selling widgets. If he sells 1 widget, it costs him $1 to produce it and he can sell it for $10. If he sells 2 widgets, it costs him $2 to produce 2 widgets, but he can only get $9 for each widget. It costs $1 to produce each widget. The average price decreases by $1 for every extra widget sold. How many widgets should sammy sell to maximise his profit?
Answer by ikleyn(52782) About Me  (Show Source):
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sammy is selling widgets. If he sells 1 widget, it costs him $1 to produce it and he can sell it for $10.
If he sells 2 widgets, it costs him $2 to produce 2 widgets, but he can only get $9 for each widget.
It costs $1 to produce each widget. The average price decreases by $1 for every extra widget sold.
ow many widgets should sammy sell to maximise his profit?
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Cost producing x widgets is x dollars.

Selling price of each one widget in the group of x widgets is 11-x.


So the profit is

    P(x) = Revenue(x) - Cost(x) = x*(11-x) - x = -x^2 + 10x.


The maximum of P(x) is at  x%5Bmax%5D = " -b%2F%282a%29 ",  where  "a"  is the coefficient
at  x%5E2,  "b"  is the coefficient at x.


In this problem,  x%5Bmax%5D = -10%2F%282%2A%28-1%29%29 = 10%2F2 = 5.


So, the optimum number of widgets in group to produce and to sell is 5.


It gives the maximum profit of -5^2 + 10*5 = -25 + 50 = 25 dollars per group.

Solved.

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On finding the maximum/minimum of a quadratic function see the lessons
    - HOW TO complete the square to find the minimum/maximum of a quadratic function
    - Briefly on finding the minimum/maximum of a quadratic function
    - HOW TO complete the square to find the vertex of a parabola
    - Briefly on finding the vertex of a parabola
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