Simple Interest

Think: I PARTY!

I = Interest
P = Principal
R = Rate
T = Time (in years)

I = PrT

In order to find the simple interest, multiply the principal (the original amount), with the rate and time. Do NOT FORGET to move over the percent (rate) twice to calculate using a decimal.

Discount and Markup

To find the discount and markup, you do one simple operation: Multiply.

The only thing that is different is the next step: Finding the sale price vs. finding the selling price after the markup

Sale Price:
1. Multiply the original price by the percent of discount (don't forget to move the decimal over twice first!)
2. Subtract (think ¨Sale Subtract) the discount from the original price.


Markup:
1. Multiply the original price by the percent of markup (don't forget to move the decimal over twice first!!)
2. ADD (think MArkup - Multiply, Add) the markup price to the original price.

You should get a cheaper cost for the SALE price and a higher cost for the new SELLING price (after markUP).


Example:

1. A $30 sweater is 30% off. Find the sale price.

Step One: Multiply $30 by 0.30 = $9.00.
Step Two: Subtract (think SALE-SUBRACT) 30 - 9 = $21.

You save $9.00 and only pay $21 for the sweater after the discount.


Example:

2. A computer store buys a computer for $120 and markups the price by 20%. Find the new selling price.

Step One: Multiply $120 by 0.20 = 24 ($24.00)
Step Two: Add (think MArkUP - Multiply, Add) 120 + 24 = $144.

The computer store will charge $144 to the customers after the markUP.

BrainPop

Here is the link!

www.brainpop.com

Fractions, Decimals, Percents

I know fractions and decimals are not the most exciting concepts to learn, but they are important.

Trust me.

Use this as an example: 100% = 1.00 = 100/100

Percent means, "out of 100."



Some tips to remember;

Change Fraction to Decimal: "top in the box"

Example: 1/2 = 1 divided by 2 = 0.5

Change Fraction to a Percent: "top in the box", Move the decimal over to the RIGHT twice.

Example: 3/4 = 3 divided by 4 = 0.75 = 75%

Change Decimal to Fraction: Look at the place value and put it over either 10, 100, 1000, or so on

Example: 0.08 = 8/100 = 2/25

Change Decimal to Percent: Move the decimal over twice to the RIGHT

Example: 0.1 = 10 %

Change Percent to a Decimal: Move the decimal over tice to the LEFT

Example: 45.7% = 0.457

Change Percent to a Fraction: Put the number over 100 and reduce, if necessary, to its simplest form.

Example: 26% = 26/100 = 13/50

Scale Drawings

The scale drawing powerpoint is posted on my EDWEB (see link on the left).
Go to 8-2; FILES; click on the folder, and see my powerpoint!

Similar Figures

Similar Figures are figures with the same shape, but not necessarily the same size.

Sometimes, you have to find the missing number of a side, but it's not that hard! All you need to do is look at the corresponding shape, look for the corresponding side, and write out a proportion!

For example:



You can try some extra practice problems on the left labeled Similar Figures

Proportions

Proportions show the equality of two ratios:

For example: 1/3 = 3/9
10/14 = 20/28

How can you find out if a proportion is equal?
There are many ways! Here are two.

1. Find the Cross Products (Cross Multiply)

Example: 1/3 = 3/9

1 x 9 = 3 x 3
9 = 9

2. Simplify either fraction and see if they are equal

Example: 10/16 = 30/48

10/16 = 5/8
30/48 = 15/24 = 5/8

So, 10/16 = 30/48


How do I set up a proportion with a WORD PROBLEM?

Example:
12 math problems in 45 min. How long does it take to do 20 math problems?

12 problems/45 min = 20 problems/x min

1. Cross multiply: 12 x x = 45 x 20

2. 12x = 900

3. Divide both sides by 12.

4. x = 75 min

CHECK YOUR WORK:

Plug in 75 into x. Are the ratios equal?


Try one on your own:

12 copies cost $0.66. Melissa needs 56 copies. How much should they cost?

............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

1. Set up the proportion:

12 copies/$0.66 = 56 copies/x

2. Cross multiply: 12 x x = 0.66 x 56

12x = 36.96

3. Divide both sides by 12.

4. x = $3.08

Did you get it right? Check your work!

Math Rap - PEMDAS

Starring Kareem and Cody

Unit Rate/Dimensional Analysis

Hello my dear 8-2's,
Today, we went over Dimensional Analysis. You can hear the Squirrel below teach a few steps, but because of limited amount of space given to speak, it'll go fast and you will need to hear it multiple times.
There is also a written explanation below, so please use that! Hope this helps!
Note: there is NO FRACTION bar in the sample problem below...just think invisibly!


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Example:

4o c/sec = ____ pints/min

1. Take the unit rate that is given:

40 c • ___ • ___
sec

2. What unit do you want to change first?

good! Pints!

So what do you need to get rid of? cups!
Where do you put cups to get rid of it? On the bottom!
What's the bigger unit? 1!
How many cups in 1 pint? 2!

40 c • 1 pint • ___
sec......2 c

3. Now that you got rid of the cups, what is the next unit you want? min!
So, what should we get rid of now? seconds!
What's the bigger unit? min!
How many seconds in 1 min? 60!

40 c • 1 pint • 60 sec
sec ......2 c....1 min

4. Multiply straight across, or cross cancel. Reduce in simplest form.

40 • 1 • 60 = 2400 = 1200 p/min
1 • 2• 1 ...... 2

and you DID IT!!! :)

Today, we learned about ratios and unit rates.

Make sure you understand that ratios can be written in three ways:

1. a/b 2. a : b 3. a to b

Don't forget to simplify if you are able to reduce a fraction:

For Example:

* * * $ $ $ $ $ $

The ratio of stars to dollar signs would be:

3 : 6 3 to 6 3/6

Since 3/6 can be reduced to 1/2, we change the ratios to:

1 : 2 1 to 2 1/2

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write a one sentence comment or question.
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Welcome to Miss Nam's blog! This site is to simply give you access to the latest news/announcements/photos in my courses! You are more than welcome to use this blog to receive extra help, ask questions, give feedback, or even help your classmates become better mathematicians!

Use this site well! It's just for you! If there's anything you'd like to see on this blog, please feel free to let me know! I'm all for changes!

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