Sunday, December 23, 2012

Holiday Fractions

Word Problems
Eli was celebrating the holidays with her family and was getting ready to pick a piece of cake to share with her friends.  If Eli wanted to get the most cake which part should she take 2/5 of chocolate cake or 3/10 of marble cake?  

Marcus sorted the recycling after a holiday gift exchange.  He found that about 1/4 paper products and 1/3 plastics.  Which type of the recyclables has the greatest amount? 

Opinion
Do you think recycling is a good idea, or do you think it is too expensive?   What are the pros and cons of recycling for you?   

Fractions in review
Here is a sheet on adding and subtracting fractions.  Remember to decide on a common denominator.  Then remember to multiply the numerator and denominator by the same number to make equivalent fractions.  

Create one of your own fraction word problems to share.  Add the answers too:)

Answers:  2/5= 4/10,  so 2/5 is a bigger piece than 3/10
1/4= 25%, 1/3=33%,  1/3 is the greater amont



   

Tuesday, December 11, 2012

Comparing World Populations

We can use population size to compare different countries in our world.  One way to write large numbers such as population is in scientific notation.  Scientific notation is written as a decimal between 1 and 9 multiplied by a power of 10.
For example the population of Turkey is 79,749,000 people, or as 7.9749 * 10^7 in scientific notation.
The country of Mexico has a population of about 114,975,000 people, or 1.14975 X 10^8.  Mexico has approximately 35 million more people than Turkey.  
Another way to compare populations is to find out the population density.  The population density compares the population to the land area.   For example Turkey has a land area of 769,632 square kilometers. When we divide the population by the land area we find the population density.  The population density tells us how many people live per square kilometer of land.  In Turkey the population density is 79,749,000 people /  769,632 square kilometers = 104 people/square kilometer.  Mexico has about 1,943,945 square kilometers of land, and its population density is 59 people per square kilometer. So, even though the population is less in Turkey, it may feel more crowded because of a higher population density.

Population density is used to compare how crowded places are around the world.  The density of a place might suggest a good place to begin a business, or a good place to advertise a product/service.   Others may think that a place with low population density may be a more peaceful place to live with less noise or traffic congestion.  How do you feel, would you prefer to live in place with a high or low population density?


Use the websites below to explore places in the part of the world you live, or places that interest you.  Here are some questions to include as you explore as you compare world populations. 

  • How do different cities or countries compare in population ? 
  • How would the populations be expressed in Scientific Notation?
  • How does the population density compare between the cities or countries?  




Quiz on Population Density

Here's an example of a Density Chart
Country

Population
(people)
Scientific Notation
(Population)
Land Area
(Square Kilometers)
Population Density
Population ÷Land Area
United States
313,847,000
3.13847 X 10^8
9,161,966
34
Mexico
114,975,000
1.14975 X 10^8
1,943,945
59
Turkey
79,749,000
7.9749 X 10^7
769,632
104
Peru
29,550,000
2.9550 X 10^7
1,279,996
23



By looking at Density I learned about the ratio of people to land area.  It was interesting to me that Turkey had the highest population density of the four countries since Turkey had the second lowest population.
 I think that this high density may be caused by it's smaller land area.  Another thing I noticed was the lowest population density was from Peru who had just 32 people per square kilometer.  The population in Peru is therefore more spread out than the other countries which have a higher density than Turkey.

References
  1. World By Map, http://world.bymap.org/LandArea.html, December 18, 2012
  2. World By Map, http://world.bymap.org/Population.html, December 18, 2012



Friday, December 7, 2012

Geometry and Right Triangles


The diagram of above shows the relationship between the area of the large purple square and the area of the middle tan colored square.  The website Math is Fun tells how how this puzzle fits together.  The right triangles and squares inside the figure create a unique pattern that we use today to find out the length of the sides of right triangles.  

Use this Pythagorean Theorem interactive tool to experiment with how the sum of the squares of the triangle legs is equal to the longest side squared.

Here's a Pythagorean Theorem problem to try. Take a moment also to share your own problem as well.
A ladder stretches from the floor to a shelf diagonally. (c)  The distance from the floor to the base of the ladder is 4 meters (b).  The height of the wall which makes a 90 degree angle with the floor is 3 meters (a).  What is the length of the ladder?

3*3  + 4*4=  ___ * ___

9  + 16  = ___ * ___

25 = ___ * ____           Hint: square root of 25 = ?
How many meters long is the ladder?