Saturday, February 23, 2013

During this week of class we learned the models for multiplication and division.
Multiplication Models

1. Repeated Addition Model
Example:
Ryan has 4 plates of cookies with 7 cookies on each plate.  How many cookies does Ryan have altogether?


For this problem I drew 4 plates (circles) and drew 7 cookies in them (green dots).  After doing so, I counted all the dots together in every plate.  I could have also multiplied 4 by 7 or add 7 together 4 times.  Just be aware of what facts the question gives you and draw it out to help you visualize it.  Then look at the question which usually involved the "total" of something.  

2. Array/Area
Example:
In the classroom there are desks lined up in 4 rows with 7 desks in each row.  How many total desks are in the classroom?

                                   

For this problem I started with labeling 4 rows with numbers.  According to the question, there are 7 desks in each row, so I counted 7 blocks and put it into each row.  In order to find the total amount I counted all the blocks that I drew out.  *For this type of problem, you usually have to use column and rows.

3. Tree/Combinations
Adam has 4 pairs of pants and 7 different shirts.  How many different outfits can he make?

To solve this problem I drew 7 shirts in a row at the top and 4 pants in a row on the bottom.  Then I drew lines connecting every shirt to every shorts.  As I was drawing the lines, I counted each line which led me to my answer.

Properties of Multiplication

1. Commutative Property

2. Associative Property

3. Identity Property
4. Distributive Property

Division Models

1. Repeated Subtraction (? * members = total)
Example: 
Meghan has $48.  She wants to give $6 to needy kids for school supplies.  How many kids can she give money to?

When I first did this problem, I drew out 48 dots in pairs of 10 and then circled groups of 6 dots.  It looks very complicated but it made sense in my mind.  I'm not sure if that is the best way to solve it, but it worked for me.

2. Partition (group * ? = total)
Example:
Meghan has $48. She wants to give an equal amount of money to 6 needy kids for school supplies. How much can she give each kid?

I solved this problem by drawing 6 circles that represents each kid.  Then I drew a line in every circle and counted up to 48 lines.  To check my work I made sure that each circle had the same amount of lines.

Area Model Practice

1. Partial Products

After learning this Partial Products Technique, I found that multiplying big numbers is actually not hard at all.  I found this way of doing multiplication a lot easier than the traditional way.  

2. Area Model

This area model is just like an Open Array model.  

3. Ratio Model
This is the one technique I found difficult.  I won't be using this technique unless I really had to.