We cover the topics in Statistics II, averages.

While we commonly use the term “average” to mean the “arithmetic mean” in statistical sense, there are other kinds of averages in statistics.

We call the data scores, and the frequency is a term used to indicate the number of times a particular score occurs. We can use a frequency table to represent data, and use a histogram to represent the table.

Apart from the arithmetic mean or just mean, which is the sum of all scores divided by number of scores, we also have:

* Mode. which is the score that occurs most often in a distribution;

* Median, which is the middle score in the list (if the list has even number of scores, the median is the average of the middle two scores).

Homework:

Page 137: #1 – #12

Math contest results are out. We have several students who won:

Richard Chang: 1st place, 5th grade

Yuheng Dong: 2nd place, 6th grade

Aaron Zhang, 3rd place, 7th grade

Congratulations!

We cover reading and drawing of pie chart, line graphs, and pictograms. This is part of Statistics I.

Again, these are topics students feel intuitive and straight forward.

With the extra time, we go over some more of the math contest results.

Homework:

Page 130: #1, 2, 3, 6, 7, 9, 13, 14

Math contest results are almost out. We are waiting for one more class’ result to finalize the final winners. We know at least two of students in our class are winners.

We start the 2nd half of the spring semester with focus on statistics, the science about collection and representing data and how to read and draw different graphs.

We first introduce different ways to represent data: bar graph, pie chart, line graph, and pictogram graph. We talk about the pros and cons of each approach.

We then talk about how to read and draw bar charts.

With the extra time left, we talked about a few questions from math contest.

Homework:

P130. #3, 4, 10, 11, 12

Plan change.

School has decided to have a school wide math contest on 4/28/2013 and all Math class students will take part in this contest. As such, we have decided to use the contest in place of the midterm exam.

So, we didn’t have the exam today. Instead we finish the chapter on transformations.

Up to now the three kinds of transformations we have talked about, Reflection, Rotation, and Translation, all do not change the figure’s shape and size. They are called rigid transformation. Today we talk about enlargement where the shape remains but the size changes. And an enlargement transformation can increase (when the scale fact is bigger than 1) and reduce (when the scale factor is less than 1) the size. And there must be a center of enlargement.

Lastly, we talked about the combination of multiple transformations and how to identify each transformation involved and fully describe it.

Homework:

Page 122: #14, #15, #17, #18, #19, #20.

This is our midterm review day, as we will have the midterm exam next Sunday (4/7/2013).

Please go over your homework for this semester to prepare for the exam.

Homework:

Page 102, Test paper 4; page 126, test paper 5

We start with measurement for spheres. Two important formulae to remember:

Volume of a sphere with radius r is: 4/3 pi r^3

Surface area of a sphere with radius of r is: 4 pi r^2

We then talk about areas of similar figures and volumes of similar solids.

In general, if the ratio of the corresponding lengths of two similar figures is a / b, then the ratio of their areas is ( a / b )^2.

And if the ratio of the corresponding lengths of two similar solids is a / b, then:

• the ratio of their volumes is ( a / b )^3;
• the ratio of their total surface areas is ( a / b )^2.

Knowing the above formulae, as well as the ones we learned last time, allows us to make various calculations in terms of finding the area or volume of some real world objects.

Homework:

Page 97: 42, 43, 44, 46, 49, 52, 53, 56, 59, 61

Today starts the Spring semester. Welcome back, old and new students.

We will be on the subject of geometry for a while. Today we covered congruent triangles. Three rules for deciding if two triangles are congruent:

1. SAS: two sides and the included angles. It is important that the angle has to be one between the two sides;

2. AAS: two angles and a corresponding side. With two angles the same, the third ones have to be identical as well. So it is important to see if the sides are indeed the corresponding ones.

3. SSS: side-side-side.

4. RHS: right angle hyptenuse and side. This one is for right-angled triangle.

We did some proof problems using the above rules.

Homework: Page 81-84, #1 – #6