Twenty-eight is 40% of
2 answers:
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Answer:
cylinder, has the least surface area
Step-by-step explanation:
We are to choose the shape that has the least surface area for the approximate volume desired. In general, the least area for the volume will be provided by a sphere, a "square" cylinder with height equal to diameter, and a cube, in order of increasing area.
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We are asked to find the area and volume of two rectangular prisms, a cylinder, and a square pyramid. Then, we are to identify the shape with the least surface area. Volume and area formulas will be used for the purpose.
<h3>Rectangular Prism</h3>The relevant formulas are ...
V = LWH
A = 2(LW +H(L +W))
for length L, width W, and height H.
<u>a)</u><u> prism 1</u>
The given dimensions are L = W = 8 in, H = 5 in. Then the volume and area are ...
V = (8 in)(8 in)(5 in) = 320 in³
A = 2((8 in)(8 in) +(5 in)(8 in +8 in)) = 2(64 in² +80 in²) = 288 in²
<u>b)</u><u> prism 2</u>
The given dimensions are L = 10 in, W = 8 in, H = 4 in. Then the volume and area are ...
V = (10 in)(8 in)(4 in) = 320 in³
A = 2((10 in)(8 in) +(4 in)(10 in +8 in)) = 2(80 in² +72 in²) = 304 in²
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<h3>Cylinder</h3>The relevant formulas are ...
V = πr²h
A = 2πr(r +h)
for radius r and height h.
c) The given dimensions are r = 5 in, h = 4 in. Then the volume and area are ...
V = π(5 in)²(4 in) = 100π in³ ≈ 314 in³
A = 2π(5 in)(5 in +4 in) = 90π in² ≈ 283 in²
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<h3>Square Pyramid</h3>The relevant formulas are ...
V = 1/3s²h
A = s(s +2H)
for base side dimension s, vertical height h, and slant height H.
d) The given dimensions are s = 10 in, h = 10 in, H = 14 in. Then the volume and area are ...
V = 1/3(10 in)²(10 in) = 1000/3 in³ ≈ 333 in³
A = (10 in)(10 in + 2×14 in) = 380 in²
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<h3>Summary</h3>The proposed figures have volume and area (rounded to the nearest unit) as follows:
The proposed <em>cylinder</em> requires the least amount of sheet metal for its construction. It has the least surface area of all of the shape choices offered.
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<em>Additional comment</em>
For a volume of 320 in³, a cube would have a surface area of 280.7 in². A "square" cylinder would have an area of 260.0 in². A sphere would have an area of 226.2 in². The above areas are somewhat larger because the shapes depart from the ideal aspect ratio.
We want to find the mean of two elements in a set, given that we know the other elements of the set and the mean of the whole set.
The answer is: -490
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For a set with N elements {x₁, x₂, ..., xₙ} the mean is given by:
Here we know that:
- The mean of the set is 0.
- The set has 1000 elements.
- 998 of these elements are ones, the other two are A and B.
We want to find the mean of the values of A and B.
First, we can start by writing the equation for the mean:
We can rewrite this as:
And we have 998 ones, then:
Now we have B isolated.
With this, the mean of A and B can be written as:
So we can conclude that the mean of the other two numbers is -490.
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