Conversions and Significant Digits

Today in class we learned about conversions and Significant digits.

Conversions are when you take something like ounces and convert it to tons. When you convert, it is usually to make things easier to count with, or to make things in larger scales to count with. When you go to the store, you obviously want to get something measured in ounces rather than tons. 
When we did the conversions we started with a chart
Convert 2.500 kilograms into milligrams
You start with 2.500 Kilograms
You know that 1 kilogram= 1000grams
You also know that 1 Gram= 1000 milligrams
so you multiply across and get 25,000,000 milligrams

When you are at home, using things like ounces, and cups are a lot easier.  When you have a conversion chart like this, it is also easy to convert to things without having to do that. Knowing how to do it is also very important in case you do not have a chart like this.

Significant digits are also very useful in every day math.  Significant numbers is pretty much a large word for rounding.  When you have a number that has a decimal you can round it to the amount of significant numbers that it has;however, you do not round when you have things like 2 arms and 2 legs, you do not have 2.1 arms, or 1.8 legs.  You use the term only in digits that you are using in math terms.

When you are looking at a decimal like 0.8904 you start at the first non-zero number on the left. 

So that decimal would have 4 significant digits.

A decimal like .00245 would only have 3 because you start counting after the two zeros. 

Here is a good conversion website to use if you are having trouble with conversion. 

Volume and Surface area

Volume and surface area are also big parts in the geometry field. 
Volume is the measure of the objects mass, its the amount of units needed to fill the object.  This is measured in units cubed.  The reason you use the units cubed is because the volume is the measure of the object being 3D.  Cubes are used because they can pack together without gaps or overlapping.  3D objects are measured in cubic inches, cubic feet, or cubic yards. 
Here is a good example of an object that is measured in cubic centimeters.
Try this volume game, it really helps with seeing how it works!

Surface area is the number of unit squares needed to cover the surface.  When doing surface area, you have to think about each face of the object that you are figuring out the area for.  when you look at an object it has two faces usually, you have to think about measuring the area of both of those sides.
Surface area formulas are also all different for each different object or shape. 
When thinking about surface area, you think about laying blocks over each face of the object and counting them up, a lot like volume and area where you are trying to measure the mass of the object, in surface area you are trying to measure the outside. 
Here is a good surface area game to play to help see what surface area really means.

Area and Perimeter

Area and Perimeter are also geometric terms to measure all figures. 

Area is the number of units it takes to cover a surface, this is usually done by squares because you have one square inch of area. When you measure in area, you square whatever unit you are using, so it would be cm squared, or inches squared, meters squared.  Area is based on the shape of the object that is being measured. When you measure a circle, you cannot use the same formula as you would a square. 
Each formula is specifically made for each object. 
Here is a area video to better understand how to calculate area. 
This gives a better idea of how you measure in square units

Perimeter is the length of the object or shape all the way around it. 
Perimeter is the measurement of the outside of the length around each part of the shape. 

When you measure perimeter you can also measure it in the same units as you do any other shape. When measuring perimeter, you can add up all sides, and that will give you the perimeter.  You do not square perimeter, you just but the cm,in,m,yd, or whatever your units may be. 

The perimeter of this shape would be 15in.







Area and Perimeter games

Systems of Measure

Systems of measurement have come a long way since the beginning of time.  People used to use hands, or feet, or arms length to measure things.  When you measured something you would say it is 5 hands long, or 6 hands long.  We have come a long way now with our English units for length that are inches, feet, yards, and miles.  When it comes to math, using the metric way is a lot easier than using the English way. 
Metric units are centimeters, meters, millimeters. 
Using centimeters is much easier because you are counting each little mark.  that stands for a point.  you can have 3.9 centimeters, whereas you would have to have 3 and 4/16ths.  It makes it much harder to have to convert them into decimals, and then add things up to get the right measurements for shapes.

When you look at the ruler you can see how much easier it is to count in centimeters. 
Measurement is used for many things, it is used to measure your body length as a baby, walls in a home, and everything else you do. 

Here are some measurement websites to help with understanding it.
http://www.aaamath.com/mea.html

Here are some good worksheets to help in your classroom with measurement.

Space Figures

In today's class we learned about space figures. 
Space figures are figures whose points do not all lie in the same plane. 
Space in geometry  is an undefined term, it is the ideas of a point, line, and plane are undefined. 
When you have a plane it moves into space of three sets, the points on the plane and two half spaces. 
The term polyhedron comes from the space figures.  The defention for polyhedron is a figure in space whose sides are polygonal regions.
A good website to learn more about space figures is this one.
Some examples of space figures and polyhedrons are:

Each one of these is apart of a space figure because all of the points on each of these has points that do not lie on the same line.

Another good website for space figures, and polyhedrons is
http://www.kidsnewsroom.org/elmer/infocentral/geometry/SpaceFigures.html

Plane Figures and polygons

Today was the start of our Geography unit, we will be learning about shapes, figures, sizes and units of measure, conversions, and significant digits.

Today I learned about Plane Figures.

A plane is a figure that is flat like the top of a table but the figure extends infinitely, planes has no thickness and has infinite ways of direction.

You can draw arrows out to infinite points in many directions.

Plane website can help you see more clearly what a plane is.

Here are some examples of some planes.

 











Polygons are also the topic from today's class.
A polygon is a simple closed curve that is the union of line segments.  Polygons are usually put into catergories based on thier number of line segments. 
To be a polygon the figure must be closed, and it must be made of line segments.
Below is not an example of a polygon:

There are only two line segments, so this does not make it a polygon.

There are also figures that are called regular polygons, these figures have all sides the same legnth, and all angles are the same.

these are examples: