Answer:
the circumference decreases by a factor 1/3.
Step-by-step explanation:
The model would be 4.05 feet long
Answer:
x = 8,49 ft
y = 4,24 ft
Step-by-step explanation:
Let x be the longer side of rectangle and y the shorter
Area of rectangle = 36 ft² 36 = x* y ⇒ y =36/x
Perimeter of rectangle:
P = 2x + 2y for convinience we will write it as P = ( 2x + y ) + y
C(x,y) = 1 * ( 2x + y ) + 3* y
The cost equation as function of x is:
C(x) = 2x + 36/x + 108/x
C(x) = 2x + 144/x
Taking derivatives on both sides of the equation
C´(x) = 2 - 144/x²
C´(x) = 0 2 - 144/x² = 0 ⇒ 2x² -144 = 0 ⇒ x² = 72
x = 8,49 ft y = 36/8.49 y = 4,24 ft
How can we be sure that value will give us a minimun
We get second derivative
C´(x) = 2 - 144/x² ⇒C´´(x) = 2x (144)/ x⁴
so C´´(x) > 0
condition for a minimum
First, find the number of females in the class. 
Then, just write the ratio. 
Really, we don't need to use that much math--we can use logic instead. Since the two congruent sides must be longer than 30in, the total has to be greater than 60in (the longest side plus the congruent sides.) So for our answer, we want the smallest total that is above sixty, which in this case is 72.44in.
Hope I helped, and let me know if you have any questions :) I can explain the real math if you want, it was just unnecessary here.
