Mark M. answered 10/03/16
Tutor
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Retired math prof. Calc 1, 2 and AP Calculus tutoring experience.
Let x = number of $10 increases
R(x) = revenue = (price)(quantity)
= (360 + 10x)(280 - 5x)
The graph of R(x) is a parabola opening downward. The x-intercepts occur when 360 + 10x = 0 and when 280 - 5x = 0. So, the x-intercepts are (-36,0) and (56,0).
By the symmetry of the parabola, the maximum revenue occurs when x is halfway between the x-intercepts. So, we have maximum revenue when x = (-36+56)/2 = 20/2 = 10.
To maximize revenue, 10 ten dollar increases are required. So, the price per bicycle should be $460. At that price, the number of bicycles sold is predicted to be 230. The maximum revenue would then be ($460/bicycle))(230 bicycles) = $105,800.