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Dmitrij [34]
3 years ago
14

A hemispherical depression is cut out from one face of a cuboidal wooden block of edge 21cm such that the diameter of the hemisp

here is equal to the edge of the cube. Determine the total surface area of the remaining block
Mathematics
2 answers:
Mandarinka [93]3 years ago
4 0

Answer:

  (2646 +110.25π) cm² ≈ 2992.4 cm²

Step-by-step explanation:

The area of a sphere is 4 times the area of a circle with the same radius. Hence the area of a hemisphere will be 2 times the area of that circle. This means carving a hemispherical depression in the face of the cube will add an area that is equal to the area of the circular hole.

Of course the total surface area of a cube is 6 times the area of one square face. The area of a circle is ...

  A = πr² = π(d/2)² = (π/4)d²

The total surface area of the carved cube is ...

  S = 6·(21 cm)² + (π/4)·(21 cm)² = (441 cm²)(6 +π/4)

  S ≈ 2992.36 cm²

The total surface area of the remaining block is about 2992.4 cm².

joja [24]3 years ago
4 0

Answer:

(2646 +110.25π) cm² ≈ 2992.4 cm²

Step-by-step explanation:

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Find the equation, (f(x) = a(x - h)2 + k), for a parabola containing point (2, -1) and having (4, -3) as a vertex. What is the s
Nataliya [291]

Answer:

f(x)=\frac{1}{2}x^2-4x+5

Step-by-step explanation:

A parabola is written in the form

f(x)=a((x-h)^2+k) (1)

where:

h is the x-coordinate of the vertex of the parabola

ak is the y-coordinate of the vertex of the parabola

a is a scale factor

For the parabola in the problem, we know that the vertex has  coordinates (4,-3), so we have:

h=4 (2)

ak=-3

From this last equation, we get that a=\frac{-3}{k} (3)

Substituting (2) and (3) into (1) we get the new expression:

f(x)=-\frac{3}{k}((x-4)^2+k) = -\frac{3}{k}(x-4)^2 -3 (4)

We also know that the parabola  contains the point (2,-1), so we can substitute

x = 2

f(x) = -1

Into eq.(4) and find the value of k:

-1=-\frac{3}{k}(2-4)^2-3\\-1=-\frac{3}{k}\cdot 4 -3\\2=-\frac{12}{k}\\k=-\frac{12}{2}=-6

So we also get:

a=-\frac{3}{k}=-\frac{3}{-6}=\frac{1}{2}

So the equation of the parabola is:

f(x)=\frac{1}{2}((x-4)^2 -6) (5)

Now we want to rewrite it in the standard form, i.e. in the form

f(x)=ax^2+bx+c

To do that, we simply rewrite (5) expliciting the various terms, we find:

f(x)=\frac{1}{2}((x^2-8x+16)-6)=\frac{1}{2}(x^2-8x+10)=\frac{1}{2}x^2-4x+5

6 0
3 years ago
hey, i have this question for algebra nation and i have no clue how to work this problem out... can you please help me?
irina1246 [14]
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3 years ago
An arch is in the shape of a parabola. It has a span of 100 feet and a maximum height of 25 ft.
faltersainse [42]

Answer:

y=-\frac{1}{100}(x-50)^2+25

the height of the arch 10 feet from the center is 24 feet

Step-by-step explanation:

An arch is in the shape of a parabola. It has a span of 100 feet, the vertex lies at the center 50 and the maximum height of 25 ft.

Vertex at (50,25)

vertex form of the equation is

y=a(x-h)^2+k, (h,k) is the center

y=a(x-50)^2+25

the parabola starts at (0,0) that is (x,y)

0=a(0-50)^2+25

subtract 25 from both sides

-25=a(-50)^2

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divide both sides by 2500

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y=-\frac{1}{100}(x-50)^2+25

the height of the arch 10 feet from the center.

center is at 50, 10 feet from the center so x=40 and x=60

y=-\frac{1}{100}(40-50)^2+25

y=24

the height of the arch 10 feet from the center is 24 feet

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alexgriva [62]
The answer would be -4 because when you add a positive and a negative it’s like subtracting.
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3 years ago
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Kobotan [32]
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