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Good Grief, Ratios?!?! PowerPoint PPT Presentation

Good Grief, Ratios?!?!. Lisa Herron – Cypress Bay High School Josh Cross – West Broward High School Jessica Flint – West Broward High School Venessa Smith – Blanche Ely High School. A ratio is an expression which compares quantities relative to each other.

Good Grief, Ratios?!?!

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Good Grief, Ratios?!?!

Lisa Herron – Cypress Bay High School

Josh Cross – West Broward High School

Jessica Flint – West Broward High School

Venessa Smith – Blanche Ely High School

• A ratio is an expression which compares quantities relative to each other.

• The most common examples involve two quantities.

Example: What is the ratio of students to pizza slices?

What is a Ratio?

2:3or or

Two students TO three slices of pizza.

The Ratio Is:

Take another look…

Or there is 1 student to 1 ½ pizza slices?

Is 2:3 the same as 1:1.5?

This is called the unit ratio.

It is often easiest to solve problems when

the unit ratio is known.

Which row will give the students the most pizza?

• Students : Pizza

Same Ratio?

If two ratios are equal then we have a proportion.

How many ice cream cones should be in row B to have same ratio as row A?

Solution

The ratio of students to ice cream is 1:2.

In row B there are 3 students:

So, we need 6 ice cream cones to have the same ratio in A and B.

Algebraically

M&M Activity

• 1. Place M&M candies along the diameter and circumference of each circle. You may have to bite an M&M to get an exact fit.

• 2. Count the number of M&M’s and fill in the table below. Write the ratio as a decimal.

• 3. Calculate the average ratio of the 4 circles.

Ratios in the Classroom

M&M Activity

• 4. What can be said about the ratio between the circumference and diameter of a circle?

Ratios in the Classroom

M&M Activity

• If the circumference of the Earth is 40,075.02 KM, and the diameter is 12,756.2 KM, how many M&Ms would be needed to go around the Equator?

What is Scaling?

- Scaling is a linear transformation that

enlarges or diminishes objects.

- For similar figures, a scale factor is

usedto make this transformation.

- A scale factor is the number by which each dimension of the original object is multiplied to find the corresponding dimension of the

model.

Applications of Ratios

The scale factor for

HO scale trains is 1:87.

Disney’s Haunted Mansion.

The map on the right shows both

the unit ratio and the scale used.

Scaling is used…

• 1. Measure the length and width of the picture.

• 2. Find the side length of one square in the picture.

• 3. Measure the length and width of the graph paper.

• 4. What scale is needed to completely fill the graph paper with the Snoopy picture?

Scaling Activity

Scaling Activity

• 5. At the top of the Snoopy picture page label the boxes alphabetically A-H. On the left side of the page, label the boxes vertically from 1-11.

• 6. On the graph paper label the boxes in the same manner.

• 7. On the graph paper, enlarge the Snoopy Picture by reproducing each corresponding box.

• 8. After you sketch the entire drawing, use a pen to outline your drawing. You may also wish to color your drawing.

Geogebra Activity

Big Idea 1

Big Idea 1

Strand 2: Polygons

Big Idea 2

Big Idea 2

Strand 4: Triangles

Strand 6: Circles