The slope of cd is 2/5
the slope of ef is -4-y/10
the lines are parallel so the slopes are equal
-4-y/10= 2/5
-4-y=2/5x10=4
-y=4=4=8
y=-8
Let us assume the length of the rectangle = x
Width of the rectangular dog run = 888 feet
Area of the rectangular dog run = 208 square feet
We already know
Area = Length * Width
Length = Area/Width
= 208/888 feet
= 0.23 feet
So the length of the rectangular dog run is 0.23 feet.
Since you have commented that
you made a mistake in giving the question so the answer will also definitely
change but the procedure will remain the same.
You need to know the dimensions first
So if we look at the cross section
and assume that the amount turned up is the same on both sides
so what we can do is make 1 equation and find the max or vertex
if the sides are legnth x and base is y
2x+y=18
and the cross sectional area is xy
2x+y=18
minus 2x both sides
y=18-2x
sub for y
x(18-2x)=areamax
18x-2x^2=areamax
we have a parabola
-2x^2+18x+0=areamax
to find the max y valie or area, we find the y value of the vertex
but the x value of the vertex is what we are looking for to find the value of x to max the area
for
ax^2+bx+c=y
x value of vertex is -b/2a
-18/2(-2)=-18/-4=9/2=4.5
4.5=x value of vertex
aswer is 4.5in
C is answer