Solve the problem.
-The revenue achieved by selling $x$ graphing calculators is figured to be $x ( 21 - 0.2 x )$ dollars. The cost of each calculator is $\$ 13$. How many graphing calculators must be sold to make a profit (revenue - cost) of at least $\$ 72.80$ ?
A) between 14 and 26 calculators
B) between 4 and 16 calculators
C) between 15 and 13 calculators
D) between 16 and 24 calculators

Question

Quizplus · Accepted Answer

The profit is given by $P(x) = x(21 - 0.2x) - 13x = 8x - 0.2x^2$. To find the number of calculators that must be sold to make a profit of at least $72.80, we solve the inequality $8x - 0.2x^2 \ge 72.80$. This inequality factors as $(x - 16)(x - 4.5) \ge 0$, so the solutions are $x \le 4.5$ or $x \ge 16$. Since the number of calculators sold must be a whole number, the only possible solutions are $x = 16$ and $x = 17$.

Solve the Problem xxx Graphing Calculators Is Figured to Be x(21−0.2x)x ( 21 - 0.2 x )x(21−0.2x)

Solve the Problem $x$ Graphing Calculators Is Figured to Be $x ( 21 - 0.2 x )$