Tuesday, April 15, 2008

Jonah's bob

What I know and learned about rectangular prisms:
We learned about getting the Surface Area and Volume of rectangular prisms. But the step we always do is making a Net.
Surface Area:
There is a lot of work to do before you can actually find out the surface area. You have to find out the area of each of the shapes. The top, front, and the left side. You only need to find out only one of each shape because each one has a pair. The right and left sides, the front and back, and the top and bottom.

The formula for figuring out the top and bottom is LxW (length x width). Since you only need to find out one of each shape all you have to do is then multiply it by 2. So it would be lxwx2 to equal the answer with a exponent of 2 (squared). E.g 3cm x 2cm x 2 = 12 2 cm.

The formula for figuring out the sides is HxW (height x width). Again, since you only need to find out only one side all you have to do is multiply it by 2. So then it would be hxwx2 to equal the answer with an exponent of 2 (squared). E.g 6cm x 2cm x 2 = 24 2 cm.

The formula for figuring out the area for the front and back is HxL (height x length). Since you only have to find out one of the shapes all you have to do is multiply the first answer by 2. So then it would be hxlx2 to equal the answer with an exponent of 2 (squared). E.g 6cm x 3cm x 2 = 36 2 cm.

Then you add all the numbers to together to get the total surface area. The exponent for surface area is always 2.

Volume:
Figuring out the volume for a rectangular prism is some what harder that find the surface area. But in some ways it is easier because you are only figuring out what is the number of the inside of the shape. There are two formulas of finding the volume.

Area of the base x Width is one of the formulas. First you find out the measurement of the base. Then you multiply that by the width because that is how many base numbers you have. E.g Base number = 15 cm 2 and the width = 3 cm. So it would be 15 cm 2 x 3 cm= 45 cm 3.

The second formula is
LxHxW (length x height x width). You first find out the measurement of the length, width, and the height. Once you do then you multiply them all together. E.g L = 5 cm
H = 10 cm W= 3cm. 5cm x 10 cm x 3 cm = 150 cm
3.

The exponent for volume is always 3.