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Help with these geometry math problems?

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I need help with:
Finding the volume of a sphere that has 8 cms of radius (v = 4\3 pi r3)

How many squared centimeters of paper is needed to cover the "superficial lateral" of a cone that has 9 cm of base and 20 of height (Sl = pi r 8)

How much paper is needed to cover the "superficial lateral" of a cylinder of 2 dm and 4 dm (Al = 2 pi rh)

How much paper is needed to cover the "superficial lateral" of a cilinder of 6cm in diameter and 15 cm height (sl 2 pi rh)

The area of a open pot which has 10 inches of diameter and 13 inches of height is = ??? (A = 2 pi r h + pi r2)
I really need these answers, its for a project im setting up. Thank you
asked Apr 16, 2013 in GEOMETRY by chrisgirl Apprentice

6 Answers

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The radius of a sphere : r = 8cms

The volume of a sphere : v = 4/3× π×r3

Substitute π= 3.14 and r = 8 in the volume v

                                         v = 4/3× 3.14× 83

                                         v = 4/3×3.14× 512

Simplify                                       

                                         v = 2138.2144cube-cms

                                         v = 2138 cube-cms (Approximately).   

answered Apr 19, 2013 by diane Scholar
Volume of the sphere is = 2145 cm^3.
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The radius of acylinder :r= diameter / 2 = 6 / 2 = 3cm

The height of a cylinder = h = 15cm

The sperficial lateral of a cylinder :sl = 2pi × r × h

Substitute the values of r and h in the sl =2pi × r × h

sl = 2× 3.14 × 3 × 15 = 282.6sq-cms.

answered Apr 19, 2013 by diane Scholar
0 votes

The radius of acylinder :r= diameter / 2 = 6 / 2 = 3cm

The height of a cylinder = h = 15cm

The sperficial lateral of a cylinder :sl = 2π× r × h

Substitute the values of r and h in the sl =2π × r × h

sl = 2× 3.14 × 3 × 15 = 282.6sq-cms.

answered Apr 19, 2013 by diane Scholar
0 votes

The radius of acylinder :r= diameter / 2 = 10 / 2 = 5inches

The height of a cylinder = h = 13inches

The sperficial lateral of a cylinder :A = (2π× r × h )+ (π × r^2)

Substitute the values of r and h in the A =(2(3.14) × 5 × 13 ) + (3.14 × 5^2)

Simplify

A = 155 × 3.14 = 486.7sq-inches.

answered Apr 19, 2013 by diane Scholar

Surface area of the open pot is 565.2 squre inches.

0 votes

5) Open pot diameter = 10 inches and height is 13 inches.

Radius of pot (r) = d/2 = 10/2

r = 5 inches.

h = 13 inches.

Formula for surface area of cylinder image

image

Substitute the above values in the formula.

image

image

image

Surface area of the open pot is 565.2 inches^2.

answered Jul 8, 2014 by david Expert
0 votes

2) If the cone is right circular cone.

Base of the cone = 9 cm

Diameter = 9 cm

Radius (r) = 9/2 = 4.5 cm

Height of the cone = 20 cm

Lateral surfface area = π r l

Where r is radius , l is slnt height of cone and π = 3.14

  • To find the slant height of cone

From pythageron therom l2 = r2 + h2

 = (4.5)2 + (20)2

= 20.25 + 400

= 420.25

l = √ (420.25)

l = 20.5 cm

Now Lateral surface area = π r l

= 3.14 * 4.5 * 20.5

= 289.665 cm^2

289.665 squred centimeters of paper is needed to cover the "superficial lateral" of the cone.

answered Jul 8, 2014 by david Expert

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