Download - [Powerpoint] Math - Measuring Area
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Shapes to be discussed:
Rectangle
Square
Parallelogram
TriangleTrapezoid
Rhombus
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The formula of finding the rectanglesarea is simply multiplying itslength/width to the other.
A = L W
where A is the area while L is the
Length and W is the width.
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Example: A rectangle has a lengthof 3 centimeters and a width of 8centimeters. Find the area.
Solution: A = L W
= (3 cm) (8 cm)
= 24 cm2
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The formula in getting a squaresarea is by multiplying the side oredge of the square with its self.
A = S or
A = S Swhere A is the area and S is the side.
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Example: A square is said to have20 cm measured as its side. Find
the area
Solution: A = S
= 20 20 cm
= 400 cm
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Any parallelogram can betransformed into a rectangle. The
formula in finding the
parallelograms area is similar tothe rectangles with the height as
the length and base as the width.
A = Base x height orA = bh
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Example: The base of a certainparallelogram is 40 cm while the
height is 20 cm. Find the area.
Solution: A = bh
= (40 cm)(20 cm)
= 800 cm
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Any side of the triangle can be thebase. The height is theperpendicular distance between
the line containing the base andopposite verses.
A = x base x height or
= bh or
= bh or
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Example: A triangles basemeasures 12 cm. Its height
measures 10 cm. Find the area.
Solution: = x base x height= x 12 x 10 cm= x 120 cm= 120/2= 60 cm
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The formula of getting the area of acube is to multiply the area of aface by six.
SA = 6e
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Example: A cube has an edge of 10cm. Find the surface area.
Solution = SA = 6e= 6(10 cm)
= 6(100 cm)
=
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To get the surface area, :
SA = 2lw + 2hw + 2hl
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Example: A microwave oven has aheight of 18 inches, width of 18 inches
and length of 30 inches. Find the
surface area.
Solution = SA = 2lw + 2hw + 2hl= 2(30)(18)+2(18)(18)+2(18)(30)= 2(540) + 2(324) + 2(540)
= 1080 + 648 + 1080=
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The lateral area, L, of a right prism isgiven by
L = hp
=(height)(perimeter)
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Example : A prism has a height of 13cm and a perimeter of 24 cm.
Find the lateral area.
Solution = L = hp=(height)(perimeter)
=(13)(24)
=
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Example : A prism has a length of 24cm and a base of 43 cm. Find thelateral area.
Solution = SA= l x 2b
= 24 x 2(43)= 24 x 86
=
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The lateral area of a regularpyramid equals half the product
of the slant height of the pyramid
and the perimeter of its base.
LA = lp
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Example : A pyramid has a lengthof 10 cm. It has a perimeter of 20
cm. Find the lateral area.
Solution = LA = lp
= (10)(20)
= 200 cm
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The surface area of a right prism isgiven by
SA = l + 2b
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The surface area of a regularpyramid is the sum of its lateralarea and its bases area.
SA = LA + b= lp + b
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Find the lateral surface area of theregular pyramid with a length of200, a perimeter of 100 and a
base of 100.
Solution = SA = LA + B
= (200)(100) + 100= 20000 + 100
=
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The lateral area of a circular coneof radius equals half the product
of the circumference of its base
and the slant height (length) ofthe cone.
LA = 2rl
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Example : Figure A is a circularcone with 30 ft as the length and
a radius of 20. Find the LA.
Solution = LA = 2rl= (2)(3.14)(20)(30)= (2)(1884)
=
3768=
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The surface area of a right circular
cylinder with radius and height equalsthe sum of its lateral area and the
area of its bases.
SA = LA + 2B = 2rh + 2r
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Example : An ice cream cone has alength of 12 cm and a radius of 2
cm. Find the surface area.
SA = rl + r
= (2)(12) + (9)
=288 ft.
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The lateral area of a right circularcylinder with radius equals the
product of the circumference of thebase and the height of the cylinder.
LA = 2rh
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Example : Find the a) LA and b) SA.
15 cm
26 cm
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a.) LA = 2 rh
= 2 (15) (26)= 780
=2449.2cm2
b.) SA = LA + 2B
= 780 + 2(225 )
= 780 + 450
= 1230
3962 2cm2