## Thursday, April 17, 2008

### Alexandra's Scribe Post

Surface Area of a Cylinder
SA= (πr²) + (2πrh) + (πr²)
The lenght of the rectangle is equal to the circumference of the circle.
Circumference (c) = πd (πxd) or 2πr (2xπxr)
radius (r) = distance (length) from the center to the outer ring.
pi (π) = is a constant and is aproximately equal to 3.14
diameter (d) = twice the length of the radius. (2r)
For example:

Volume of a Cylinder

Volume of a cylinder = area of base x height or πr² x h

For example:

### Ivanne's Scribe Post

CIRCUMFERENCE OF A CIRCLE...

Circumference (C) is the distance around the outer ring.
C = Pi x d or Pi2r/2Pir

Pi is a constant and is approximately equal to 3.14.
Picture

Example

Radius (r) is the distance from the center to the outer ring...
Picture

The diameter (d) of circle is twice the length of the radius...
D = 2 x r or 2r

Picture

Example

AREA OF A CIRCLE...
Area = Pi x r²
Pi = 3.14
Radius is the distance/length from the center to the outer ring...
Picture

Example

**just remember the formulas and it would be easy...

## Wednesday, April 16, 2008

### Kevin T's Scribe

Todays class is about the surface area of a cylinder.

The Net of a cylinder

the cylinder has 3 shapes, 2 circles and a rectangle. To get the surface area of a cylinder follows this formula:

SA = (Pi x r²) + (2 x Pi x r) + ( Pi x r²)

In class we had a an example question: the height is 10 and the radius is 5. The circumference is the length of the rectangle so you get the area of the 3 shapes and add them together to ge the Surface area.

SA = (3.14 x 25) + (2 x 3.14 x 5) + ( 3.14 x 25)
= 78.5 + 314 + 78.5
= 417

## Tuesday, April 15, 2008

### alexandra's BOB

Surface Area & Volume of a Rectangular Prism

Surface Area
S.A. = 2 (h x L) + 2 (L x w) + 2 (h x w)
h = 5cm
L = 10 cm
w = 2 cm

2 (5cm x 10cm) + 2 (10cm x 2cm) + 2 (5cm x 2cm) = 160cm²

WHY IS IT A SQUARED CM?
-The surface area of a rectangular prism is measured as SQUARED CM because a surface area has 2 dimensions.

Volume
V = L x w x h
L = 10cm
w = 2cm
h = 5cm

10cm x 2cm x 5cm = 100cm³
According to commutative property of multiplication, the order of the numbers that we multiply doesn't matter. That means, if you mix up the numbers, you'll still get the same answers.
eg: 10 x 2 x 5 = 100cm³
2 x 5 x 10 = 100cm³
5 x 2 x 10 = 100cm³

Here's another way:
(L x w) x h = Volume
(10cm x 2cm) x 5cm = 100cm³
(2cm x 5cm) x 10cm = 100cm³

WHY IS IT A CUBIC CM?
-The volume of a rectangular prism is measured as CUBIC CM because the volume of a certain rectangular prism has 3 dimensions.

### Melissa's Bob

In this bob I will be showing you about the surface area and the volume of a rectangular prism.....
The Surface Area.....
- How to find the top and bottom?
A= (LxW) + (LxW)
-How to find the front and back?
A=2(HxW)
- How to find the sides ?
A= 2(HxW)( This is the net of the rectangular prism looks like)

- To solve a for the surface area the you have to use a formula and the formula is....

2(Lxw) + 2(HxL) + 2(HxW) = SA
- example:
H=2 cm
L= 3 cm
W= 4 cm
2(LxW) + 2(HxL) + 2(HxW) = SA
2(3 cm x 4 cm) + 2( 2 cm x 3 cm) + 2( 2 cm x 4 cm)
12 cm x 12 =144 cm
6 cm x 6 cm=36 cm
8 cm x 8 cm=64 cm
144 + 36 + 64 = 244 cm
SA = 244 cm squared

The volume.......
- The volume's formula is very simple ...
(LxW) x H
-example

L= 2 cm
H= 3 cm
W= 4 cm
v=(LxW) x H
v=(2 cm x 4 cm) x 3 cm
v=8 cm x 3 cm
v=24 squared cm

Finding the surface area of a cube and a rectangular prism,needs the illustration of the net and solve the problem based on the formula. in getting the volume also need formula. good thing in cubes are that they have same sides.

To represent this objects, we need to illustrate 3d images

Getting the surface area of a cube.

3d cube SA formula of the surface area of a cube

Solution in getting the surface area of a cube. i did this because it is easier. since cube has 6 sides with equal area, i multiplied each side with the same area to the number of sides that make up a cube.

Net of a cube

Getting the
volume of a cube

formula of getting the volume of a cube. It can also be used in a rectangular prism.

the area of the base times height is commonly used in getting the volume of many shapes including triangular pyramids and excluding irregular shapes (i guess) Getting the volume of a cube or a rectangular prism is very easy. just multiply the area of the base, or length times width, then multiply it to the height.

In getting the volume of a rectangular prism, the formula is still the same, the formula is a lifetime formula.

Getting the volume of a rectangular prism

In this example, same formula is used and just solve it, the unit of the answer or the volume is called cubic centimetres

Getting the Surface area of a rectangular prism

As said, the formula is 2(lw)+2(hl) + 2(hw). it is the very common in getting the surface area of a rectangular prism.
by the way, the variables stands for:
l-length
w-width
h-height

net of a rectangular prism

### Jomarie's BOB

This BOB is all about how to find the volume and surface area of a cube and a rectangular prism.
Also the net of the 3-D object.

The step to finding out the surface area of a cube.

The Net

Example

Surface Area = 6(2cmx2cm)
= 24cm2

The step to finding out the volume of a cube
How to get the volume of a cube:
(LxWxH)

Example

L(2)xW(2)xH(2)
=2x2x2
=8cm3

The step to finding out the surface area of a rectangular prism

The Net

Example

Surface Area=

4(2cmx6cm) = 48cm2
+
2(2cmx2cm)
= 8cm2
______________________
56cm2

The step to finding out the volume of a rectangluar prism

(LxWxH)
L(2)xW(2)xH(6)
=2x2x6
=24cm3

### Ivanne's BOB

For this BOB, I will show you what I know about getting the surface area and volume of a rectangular prism...

SURFACE AREA...
In getting the surface area, you should know the formula on how to get the area of each side...Just remember that the front and back sides, the top and bottom sides, and the left and right sides have the same size or measurements...

Formula on how to get the area of the:
FaB = 2(Lxh)
TaB = 2(LxW)
LaR = 2(hxW)

L = 10 cm
h = 8 cm
W = 6 cm

FaB = 2(Lxh)
= 2(10 cm x 8 cm)
= 2(80 cm2)
= 160 cm2
TaB = 2(LxW)
= 2(10 cm x 6 cm)
=2(60 cm2)
= 120 cm2
LaR = 2(hxW)
= 2(8 cm x 6 cm)
= 2 (48cm2)
= 96 cm2
After you get the area of each side, you will add them all up...*You will times them by 2 since they have the same size...

SA = 160 cm2 + 120 cm2 + 96 cm2 = 376cm2

VOLUME...
In getting the volume, you just have to follow a simple formula...which is, LxWxh...

LxWxh
15 cm x 5 cm x 10 cm
750 cm3 = volume..

**sorry for the small pictures and some (or all) of the measurements actually don't look right for their sizes..

### Angelo's B.O.B

This blog is about the steps to find the surface area and the volume for a cube and a rectangular prism. When doing work for a cube or a rectangular prism you need to include the 3D diagram and their net.

This is the 3D version of a cube :

This is the cube's net :

This is an example of a rectangular prism :

This is it's net :

There are several ways to find a surface area for both of the shapes. One way for the cube is this :

It is clear that if you get the areas of each square in the cube you already can solve the surface area of the cube. You can solve the area of each side by multiplying the two different measurements that make the side. For example, if one side is made up by 2 lengths and 2 widths, you multiply the width and length together to get the area. So if you already have all the areas, just add all six sides together and get the Surface Area.

There are two steps used to solve both of the shapes. I used one of them on the cube.

All you have to do is find the base and multiply that answer with the height. To find the "base" of a shape, all you have to do is multiply it's length with the width.

Now moving on to the rectangular prism. The step I used for this shape can also be used on a cube.

This step take more time. If you multiply length and width, you are finding the area for the Top or the Bottom parts of the shape. If you multiply length and height, you are finding the area for the Front or Back. And if you multiply width and height, you obviously get the area for one of the two sides. Since there are six sides. Once you find the area for one side of the shape, times it by two to get the other side. For example, if you find the area for the Top, just multiply it by two so you can get the area for the Bottom also.
Yes, these steps on finding the volume of a rectangular prism can also be used to find the volume of a cube :

This explanation is quite simple. If you multiply the length and width, find the answer and multiply that to the height. Once your done that, you have solved the volume.

Now...you guys should know how to find the Surface Area and the Volume of a Cube and also a Rectangular Prism.

### jordan's bob

On this bob I'll be explaining how to get the surface area and volume of a cube and a rectangular prism and I'll also show you the net.
this is a cube:
L = length
H= Height
W= Width

this the net of a cube

how to find the surface area and volume of a cube.
To get the surface area of a cube first you have to find all the area of the squares in the net.
the cube has a equal sides, if all sides was 3 cm you just have to find the area of one box and all the box are the same.
like this:
you just have to add all the area.
9cm2 + 9cm2 + 9cm2 + 9cm2 + 9cm2 + 9cm2 = 54cm2
or
SA= 6 (9cm2)
= 54cm2

or
S.A=2(l x W) + 2(h x l) + 2(h x w)

Volume
Formula:
V=L x W x H
V=(3cm x 3cm )x 3cm
V=9cm x 3cm
V=27 cubic cm
Rectangular prism.

This is the net of rectangular prism looks like:
to get the surface area of rectangular prism you need to use the formula:
SA= 2 (l x w) + 2 (h x w) 2 + (h x l).

L = 5cm, W = 2cm, H = 6cm

SA= 2 (l x w) + 2 (h x w) + 2 (h x l)
SA= 2 (5cm x 2cm) + 2 (6cm x 2cm) + 2 (6cm x 5cm)
SA= 2 (25cm squared) + 2 (36cm squared) + 2 (30cm squared)
SA=625cm squared + 1296cm squared + 900cm squared
SA=2821cm squared

Volume formula:
V=(L x w)H
V=(5cm x 2cm)6cm
V=25cm x 6cm
V=150 cubic cm

### CARL's BOB

HOW TO SOLVE THE SURFACE AREA AND VOLUME OF A RECTANGULAR PRISM:

A rectangular prism has 2 ends and 4 sides. Opposite sides have the same area. The surface area is the sum of the areas of all six sides.
How to find the surface area of Rectangular Prisms:
Find the area of two sides (Length x Height)2 sides
Find the area of adjacent sides (Width x Height)2 sides
Find the area of ends (Length x Width)2 ends
Add the three areas together to find the surface area
Example: The surface area of a rectangular prism 5 cm long, 3 cm. wide and 2 cm. high = (5 x 2)2 + (3 x 2)2 + (5x 3)2 = 20 + 12 + 30 = 62 cm2.

volume has a simple formula
v=lxwxh
v=5cmx3cmx2cm
v=30cm3

### Jenna's BOB

What i know all about surface area and the volume of a cube and rectangular prism:

Surface Area (SA): The extent of a 2-dimensional surface enclosed within a boundary.
Volume (V): The amount of space that and object or substance occupies.

To find out the surface area, first you have to make it into a net.
Find out the area of the top and bottom (L x W)
Find out the area of the front and back (H x L)
Find out the area of the sides (H x W)

To find out the Volume, you use the formula L x W x H

L = 5cm

W = 3cm
H = 10cm
- 5cm x 3cm x 10cm
V = 150 cubic cm