Showing posts with label Area of Prism. Show all posts
Showing posts with label Area of Prism. Show all posts

Friday, January 25, 2013

Surface Area of Prisms and Cylinders

Introduction about prism and cylinder:

Prism:

In geometry, an n-sided prism is a polyhedron made of an n-sided polygonal base, a translated copy, and n faces joining corresponding sides. Thus these joining faces are parallelograms

Cylinder:

A cylinder is one of the most basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given straight line, the axis of the cylinder.

(Source – Wikipedia)


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Formula Used to Find the Surface Area of the Prism and Cylinder:

Rectangular prism:

Surface area of the rectangular prism (A) = 2(wh + lw + lh) square units

w – Width

h – Height

l – Length

Triangular prism:

Total Surface Area of the triangular prism (T.S.A)

T.S.A = L.S.A + 2 x Base Area

Total surface area T.S.A = (P x h + 2 A) sq. units

P - Perimeter

A - Area of the base

h - Height of the prism

Cylinder:

Surface area of cylinder (SA) = 2 p r^2 + 2 p r h square units

r – Radius

h – Height

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Surface Area of Prisms and Cylinders - Example Problems:

1. The rectangular prism has the length 25 cm, width 13cm and height 10 cm. find the surface area of the rectangular prism.

Solution:

Given:

Length (l) = 25 cm

Width (w) = 13 cm

Height (h) = 10 cm

Formula to find the surface area of the rectangular prism:

Surface area (A) = 2(wh + lw + lh) square units

= 2 (13 x 10 + 25 x 13 + 25 x 10)

= 2 (130 + 325 + 250)

= 2 (705)

= 1410

Surface area of the rectangular prism (A) = 1410 cm 2

2. The triangular prism has the base side length 3 cm, 4cm and 5 cm. its height is 10 cm. find total surface area of prism.

Solution:

Given:

Three side length of triangular prism = 3 cm, 4 cm, 5 cm

Height of the prism = 10 cm

Base of the triangle = 3 cm

Height of the triangle = 4 cm

The lateral surface area of the prism = p x h square units

= (3 + 4 + 5) x 10

=12x10
L.S.A =120 cm2

Now the area of the bases, A = 1/2 bh square units

h is the height of the triangle

= 1/2 x 3 x 4

A= 6 cm2

The total surface area of the prism = p h + 2 A square units

= 120 + 2 x 6

Total surface area of the prism  =  1440 cm2

3. The cylinder has radius r = 3 cm, h= 12 cm. Find the surface area of cylinder.

Solution:

Given:

r= 3 cm

h=12 cm

Geometric Formula:

The surface area of the cylinder  = 2 p r^2 + 2 p r h square units

= 2 x 3.14 x 32 + 2 x 3.14 x 3 x 12

= 56.52 + 226.08

The surface area of the cylinder = 282.6 cm2