4-3 Percents And Proportions

Warm-up Monday, October 26, 2009 Find each product. a)

b)

c)

d)

0.6 •9 = 3.8 •6.8 = 23 20 • = 60 46 17 5 • = 135 34

Proportions and Percent Equations Section 4-3 We will be able to find parts of wholes and percents or finding whole amounts

Basic Idea For tonight’s homework, you will see problems like these: 1. 2. 3.

What percent of 15 is 5? What is 12% of 60? 28 is 14% of what number?

We’ll use key words to solve these problems.

Basic Idea One very easy phrase to remember to solve these problems correctly is this: “Percent over one hundred equals is over of” It looks like this:

% is = 100 of

Let’s Try (examples) Let’s give it a try. 1.

What percent of 15 is 5?

% is = 100 of

so

x 5 = 100 15

Example 2 2.

What is 12% of 60?

% is = 100 of

so

12 x = 100 60

Example 3 3.

28 is 14% of what number?

% is = 100 of

so

14 28 = 100 x

Note on Language Sometimes the book uses different language in its tool. It would use the phrase “percent over 100 equals part over whole”. It’s the same thing with different words. In this phrase “is” becomes “part” and “of” becomes “whole”.

Summary From page 317 (321) in your book.

Homework 

Please complete page 200: 1 – 19 all

Ticket to leave a)

b)

c)

What percent of 90 is 27? Find 25% of 480. What covers about 361,736,000 km2, or about 70.8% of the earth’s surface. Approximately, what is the total surface area of the earth?