Mr. Ohashi's Math 8 Website

Eighth Grade Math at Eckstein Middle School

Monday, 4/30: Dilations (Day 2 of 12)

Learning Target: Perform dilations on shapes to stretch and shrink them.
Handouts: Dilations (Turn in: Tues, 5/1)

We started today by writing down the coordinate rules for reflections and translations (slides). We found that you can easily find where a point will be when it is either reflected or translated:

Today, we learned a new transformation called a dilation. When we perform a dilation, the image has the same shape but is a different size than the original! When drawing dilations, you have to know two things… the scale factor and the center of dilation. The center of dilation is where everything is based out of. The scale factor is how many times bigger (or smaller) you are making the shape. To draw the dilation, count the distance from the center of dilation to a point on the shape. Multiply that distance by the scale factor, and then plot it!

Here is a video explaining the steps:

Here are the notes and examples we wrote down:

While working on the classwork, you should have discovered the coordinate rule for dilations centered at the origin. Just multiply the original coordinates by the scale factor!

Your homework is to finish #1-4.

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Friday, 4/27: Reflections & Translations (Day 1 of 11)

Learning Target: Draw reflections and translations of an image on a grid.
Handouts: Reflections & Translations (Turn in: Mon, 4/30)

We started a new unit today on transformations. A transformation is basically when you take a figure and make a copy of it somewhere. Sometimes the figure will be the exact same shape and size, and sometimes it won’t be. This is a very visual unit and most kids find it to be the easiest unit.

There are four types of transformations, but two that we learned about today are reflections and translations. Most of you know all about reflections, because you look into a mirror and see your reflection everyday! The key to drawing an object’s reflection is to pay attention to where your line of reflection is (think of it as the mirror). The reflection of each point is the same distance from the line of reflection, but on the opposite side!

A translation is when you slide a shape over! It is the easiest transformation of the four, because all you have to do is slide each point the stated distance and directions, and then connect the points.

Here are the notes that we took:

When drawing transformations, make sure that you label the points and include prime marks on your new points. The prime marks signify that the point is a copy, and not the original point!

You should have finished #1-2 in class. Have a great weekend!

Thursday, 4/26: Grade-Level Review

Learning Target: Review grade-level concepts.
Handouts: Grade Level Review

We had one more day of grade-level review, since many kids needed more time to finish their SBA testing.

You got a packet today and will turn it in the next time I see you. You do not have to finish the entire packet, but you can if you’d like! There is no homework tonight!

Wednesday, 4/25: Grade-Level Review

Learning Target: Review grade-level concepts.
Handouts: Grade Level Review

We are spending Monday, Tuesday, and Wednesday doing some grade-level review. This will give you a chance to review the concepts that you will need to know on the Math SBA in three weeks!

You got a packet today and will turn it in the next time I see you. You do not have to finish the entire packet, but you can if you’d like! There is no homework tonight!

Tuesday, 4/24: Grade-Level Review

Learning Target: Review grade-level concepts.
Handouts: Grade Level Review

We are spending Monday, Tuesday, and Wednesday doing some grade-level review. This will give you a chance to review the concepts that you will need to know on the Math SBA in three weeks!

You got a packet today and will turn it in the next time I see you. You do not have to finish the entire packet, but you can if you’d like! There is no homework tonight!

Monday, 4/23: Grade-Level Review

Learning Target: Review grade-level concepts.
Handouts: Grade Level Review

We are going to spend Monday, Tuesday, and Wednesday doing some grade-level review. This will give you a chance to review the concepts that you will need to know on the Math SBA in three weeks!

You got packet #1 today and will turn it in the next time I see you. You do not have to finish the entire packet, but you can if you’d like! There is no homework tonight!

Friday, 4/20: Data Quiz (Day 10 of 10)

Learning Target: Take a quiz on scatter plots and two-way tables.
Handouts: After the Quiz (Turn in: Mon, 4/23)

We had a quiz today! Your homework was the After the Quiz worksheet. Have a great weekend!

Thursday, 4/19: Data Quiz Review (Day 9 of 10)

Learning Target: Review data work in order to get ready for the quiz.
Handouts: Data Quiz Review (Turn in: Fri, 4/20)

We have a quiz tomorrow, so today was a quiz review day!

For the quiz, you should be able to:
• Make, read, and interpret a scatter plot
• Make, read, and interpret a two-way table

Your homework is to finish the rest of the Quiz Review. Remember, you have to have the Quiz Review completed to take the Quiz!

Wednesday, 4/18: Class Data (Day 8 of 10)

Learning Target: Use relative frequency (percents) to compare data in two-way tables.
Handouts: Looking at Our Class Data (Turn in: Thurs, 4/19)

Today, we collected data from our own class and analyzed it. We had four questions that we were trying to answer:

  • Do boys play more video games than girls?
  • Do kids who use their planner get better grades?
  • Does doing your homework lead to better test scores?
  • Do kids who eat breakfast perform better during first period?

 
Each class period had a different set of data. You can access your class’s data here:
3rd Period Data
4th Period Data
5th Period Data

Your homework is to finish #1-3. Don’t forget that we have a quiz on Friday!

Tuesday, 4/17: Analyzing Two-Way Tables (Day 7 of 10)

Learning Target: Use relative frequency (percents) to compare data in two-way tables.
Handouts: Analyzing Two-Way Tables (Turn in: Wed, 4/18)

The whole point of making these two-way tables and relative frequency two-way tables is to analyze data and make conclusions about the information. That was our focus today.

Remember, the focus of your conclusion will depend on which relative frequency table that you are writing about. Look at the examples from our notes:

The percents in the first table are based on gender, so first pick a gender column. Then, look at the data in the column to see what it tells you. For example, if I chose boys, then I could say “Boys like scary movies. I know this because 75.7% of boys like scary movies.” If I chose girls, then I could say “Girls are split pretty evenly about scary movies. I know this because 52.2% of girls like scary movies and 47.8% of girls don’t.”

The percents in the second table are based on opinions of scary movies, so first pick a row about scary movies. If I chose liking scary movies, then I could say “Kids who like scary movies are mostly boys. I know this because 70% of the kids who like scary movies are boys.” If I chose not liking scary movies, then I could say “Kids who do not like scary movies are split pretty evenly among boys and girls. I know this because 55% of kids who don’t like scary movies are girls and 45% are boys.”

To justify your statement, use data from the relative frequency table. In other words, use the percentages!

Your homework is to finish #1-4. Don’t forget that we have a quiz on Friday!

Monday, 4/16: Relative Frequency Tables (Day 6 of 10)

Learning Target: Use relative frequency (percents) to compare data in two-way tables.
Handouts: Relative Frequency Two-Way Tables (Turn in: Tues, 4/17)

We continued our work with two-way tables again today, but it got a little bit harder. We have found that it is difficult to compare data in two-way tables because different columns and rows have different total amounts. So that we can have comparable amounts, we can change them into percents (relative frequencies)! The examples that we did in our notes are based on the two-way table we did a few days ago.

Just like we can read the table in different ways to find percents, we can make a two-way relative frequency table in different ways to show the percents. There were three kinds of relative frequency tables in today’s assignment. One where you used the total number of people surveyed to find the percents (then all of the percents should add up to 100%). Another was where you used the total in each column to calculate the percents (then each column should add up to 100%). And the last was where you used the total in each row to calculate the percents (then each row should add up to 100%).

If you would like to watch a video explaining it, watch this:

Your homework is to finish #1-3. We have a quiz on Friday to wrap up this unit!

On Wednesday, we are going to gather data from our class! Make sure that you know about how long per day that you play video games, your 3rd quarter Language Arts grade, and your 3rd quarter grade in your first period class.

Friday, 4/6: Two-Way Tables (Day 5 of 10)

Learning Target: Use two-way tables to summarize and analyze data.
Handouts: More Two-Way Tables (Turn in: Mon, 4/16)

We did more work with two-way tables today! We did #1 together in class and learned how to turn a table of data into a two-way table.

You should have finished #1-6 in class – if not, then you have homework! Have a great Spring Break!

Thursday, 4/5: Two-Way Tables (Day 4 of 10)

Learning Target: Use two-way tables to summarize and analyze data.
Handouts: Two-Way Frequency Tables (Turn in: Fri, 4/6)

So far for this unit, we have been comparing two sets of numerical data (data that is made up of numbers) in scatter plots. Today, we learned how to compare two sets of categorical data (data this is made up of words). We can accumulated and organized the categorical data into a two-way table. Here are the notes that we took:

We can fill in the table by using the information in the story and logic. Two-way tables are called “two-way” tables because you can read them in two different ways. Reading the table vertically, you see we are looking at girls and boys. Reading the table horizontally, you can see that we are looking at kids who like scary movies and kids that don’t. We can use the table to answer questions:

What percent of girls like scary movies?
Since there were a total of 23 girls and 12 of them like scary movies, 12 ÷ 23 ≈ 52.1%.

What percent of kids who like scary movies are girls?
Since there are a total of 40 kids who like scary movies and 12 of them are girls, then 12 ÷ 40 = 30%.

Notice that the two above questions are slightly different! The first one reads the table vertically and the second one reads the table horizontally. They also give two totally different percentages!

Your homework is to finish #1-6.

Wednesday, 4/4: Understanding Scatter Plots (Day 3 of 10)

Learning Target: Use scatter plots to explore the relationship between two variables.
Handouts: Understanding Scatter Plots (Turn in: Thurs, 4/5)

Our focus today was on understanding what scatter plots tell us about the relationship between the variables. When a scatter plot shows a positive association, it means that as one variable increases so does the other one! When it shows a negative association, it means that as one variable increases the other decreases!

We also focused on what the equation for the line of best fit tells us. The y-intercept gives us information about the starting value of one the variables, and the slope tells us the rate of change.

For 3rd period, your homework is to finish #1-6. For 4th and 5th periods, your homework is to finish #1-3.

Tuesday, 4/3: Scatter Plots (Day 2 of 10)

Learning Target: Use scatter plots to explore the relationship between two variables.
Handouts: More with Scatter Plots (Turn in: Wed, 4/4)

Today we continued with scatter plots, but this time we added something… you had to find and use the equation for the line of best fit! Here is the example that I showed you in class:

When finding the equation for your line of best fit, keep the following things in mind:

  • The scale may or may not be going up by 1’s, so pay attention to it!
  • When picking two places on your line for the slope, pick two places far away from each other! This will help make your slope more accurate and make the margin of error from estimating a lot smaller.
  • List the slope as a decimal instead of a fraction. This makes it easier for us to compare slopes and it will make it easier for you to compute with it!

In class, you should have finished at least #1-5. For #3, make sure that you write the equation into your notes so that you can refer to it later! Your homework is to finish #1-5.