The area is:
A = x * y = 20000
The cost function is:
C = 2.50 (2x) +3.50 (2y)
Rewriting we have:
C = 5x + 7y
Writing as a function of x we have:
C = 5x + 7 (20000 / x)
Rewriting:
C (x) = 5x + 140000 / x
We derive:
C '(x) = 5-140000 / x ^ 2
We equal zero and clear x:
0 = 5-140000 / x ^ 2
140000 / x ^ 2 = 5
x ^ 2 = 140000/5
x = root (140000/5)
x = 167.33 feet
Therefore the cost is:
C (167.33) = 5 * (167.33) + 7 * (20000 / 167.33)
C (167.33) = 1673.32 $
Answer:
The cost of the least expensive fence is:
$ 1673.32
Answer:
around 10k. just look at the graph where the 4 and line of graph meet (edit: I didn't see the choices, it's C
The word problem only gives you two numbers, so it would be easy to assume that the questions involves those two numbers. However, in this case, the question requires that you calculate another answer first: the number of questions Abel got right. You'll need to subtract 4 from 80, then calculate the percentage of the difference:
80-4=78, and 78/80*100=97.5 percent So it will be 50
