Sienna has 80 yards of fencing to enclose a rectangular area. Find the dimensions that maximize the enclosed area. What is the m

aximum area?

Mathematics

1 answer:

Lubov Fominskaja [6]3 years ago

7 0

$2x+2y=80\ \ \ /:2\\\\2x:2+2y:2=80:2\\\\x+y=40\ \ \ /-x\\\\y=40-x\ \ \ (D_x:x\in(0;\ 40))$

$Area=xy\\\\substitute\ y=40-x\\\\Area=x(40-x)=-x^2+40\\(it's\ quadratic\ function\ where\ a=-1;b=40;c=0)\\\\vertex\ of\ parabola:p=\frac{-b}{2a}\to p=\frac{-40}{2\cdot(-1)}=\frac{-40}{-2}=20-it's\ max\\\\x=20\ then\ y=40-20=20\\\\Answer:dimensions\ of\ rectangular\ is\ 20\ yd\ \times\ 20\ yd,\\and\ area\ is\ 20^2=400\ yd^2.$

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The Lewis family and the Perry family each used their sprinklers last summer. The water output rate for the Lewis family's sprinkler was 15 L per hour. The water output rate for the Perry family's sprinkler was 40 L per hour. The families used their sprinklers for a combined total of 65 hours, resulting in a total water output of 1850 L . How long was each sprinkler used

Answer:

Hours of use of sprinkler by Lewis family is 30 hours.

Hours of use of sprinkler by Perry family is 35 hours.

Step-by-step explanation:

Let W = hours of use by Lewis family

65 - W = hours of use by Perry family

Then;

15W + 40*(65 - W) = 1850

15W + 2600 - 40W = 1850

(15 - 40)W = 1850 - 2600

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W = 750/25 = 30

Therefore;

W = 30

65 - W = 65 - 30 = 35

Hence,

Hours of use by Lewis family is 30 hours.

Hours of use by Perry family is 35 hours.

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