Question

The function C(x)=−20x+1681 represents the cost to produce x items. What is the least number of items that can be produced so that the average cost is no more than $21?

Answer 1

Answer:

The least number of items to produce is 41

Step-by-step explanation:

Average Cost

Given C(x) as the cost function to produce x items. The average cost is:

$\displaystyle \bar C(X)=\frac{C(x)}{x}$

The cost function is:

$C(x) = -20x+1681$

And the average cost function is:

$\displaystyle \bar C(X)=\frac{-20x+1681}{x}$

We are required to find the least number of items that can be produced so the average cost is less or equal to $21.

We set the inequality:

$\displaystyle \frac{-20x+1681}{x}\le 21$

Multiplying by x:

$-20x+1681 \le 21x$

Note we multiplied by x and did not flip the inequality sign because its value cannot be negative.

Adding 20x:

$1681 \le 21x+20x$

$1681 \le 41x$

Swapping sides and changing the sign:

$41x \ge 1681$

Dividing by 41:

$x\ge 41$

The least number of items to produce is 41