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
the discount is 22.5 * .2 =
round 22.5 to 20
20 *.2
Choice B
Answer:
<em>She invested 1600 at 8% (to get the shown $160 interest)</em>
<em>and $7400 at 10% (to get the shown 640 interest)</em>
<em>If x = 4000 then $80 interest is x2 again = $160</em>
<em>and so forth $320 interest x 2 again = $640</em>
Step-by-step explanation:
<em>The format would always be for x and then where </em>
<em>investment - x = interest we can work out totals this way and find x.</em>
<em>9000-x = 800 is first equation and substituted into 2nd equation;</em>
<em>0.10x+0.08(9000−x)=800</em>
<em>Use the distributive property to multiply 0.08 by 9000−x.</em>
<em>0.10x+720−0.08x=800</em>
<em>Combine 0.10x and -0.08x to get 0.02x.</em>
<em>0.02x + 720 = 800</em>
<em>Subtract 720 from both sides.</em>
<em>0.02x=800−720</em>
<em>Subtract 720 from 800 to get 80.</em>
<em>0.02x=80</em>
<em>Divide both sides by 0.02.</em>
<em>x= 80 / 0.02</em>
<em>Make decimals numbers = 1 or above.</em>
<em>80 / 0.02 x 100</em>
<em>x= 8000 / 2</em>
<em>x = 4000</em>
