Answer:
- 12 ft parallel to the river
- 6 ft perpendicular to the river
Step-by-step explanation:
The least fence is used when half the total fence is parallel to the river. That is, the shape of the rectangle is twice as long as it is wide.
72 = W(2W)
36 = W²
6 = W . . . . . . the width perpendicular to the river
12 = 2W . . . . the length parallel to the river
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<em>Development of this relation</em>
Let T represent the total length of the fence for some area A. Then if x is the length along the river, the width is y=(T-x)/2, and the area is ...
A = xy = x(T -x)/2
Note that the equation for area is that of a parabola with zeros at x=0 and at x=T. That is, for some fence length T, the area will be a maximum at the vertex of this parabola. That vertex is located halfway between the zeros, at ...
x = (0 +T)/2 = T/2
The corresponding area width (y) is ...
y = (T -T/2)/2 = T/4
Equivalently, the fence length T will be a minimum for some area A when x=T/2 and y=T/4. This is the result we used above.
Answer:
D.) A cube that is 1 inch long, 1 inch wide, and 1 inch high
Step-by-step explanation:
A unit cube, more formally a cube of side 1, is a cube whose sides are 1 unit long. The volume of a 3-dimensional unit cube is 1 cubic unit, and its total surface area is 6 square units.
⭐ Answered by Kakashi ʕ •㉨• ʔ⭐
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Answer:
A
Step-by-step explanation:
The volume of a pyramid is one third the height times the area of the base.
V = ⅓ h A
The base is a square, so the area is the width times length.
V = ⅓ h wl
Problem is, we don't know the height, only the slant length. But we can use this to find the height.
If we cut a cross section down the middle of the pyramid, we get an isosceles triangle. The base of the triangle is 24, and the legs are 37.
If we cut this triangle in half, we get two right triangles. Each right triangle has a base of 12 and a hypotenuse of 37.
Now we can use Pythagorean theorem to find the height of the triangle, which is also the height of the pyramid.
c² = a² + b²
37² = 12² + h²
h = 35
Now we can find the volume. h = 35, w = 24, and l = 24:
V = ⅓ h wl
V = ⅓ (35) (24) (24)
V = 6720
So the volume is 6720 ft³, or answer A.
