Reteach Unit 3b Scale and Slope

Unit 3b Test Prep

Let's figure out how to do this math!
Please work through each slide :)
You got this!

To make a scaled copy of a shape, multiply all the lengths in the original figure by the same number. 

The number you multiply by is the scale factor.

Review
scale factor

For example, the original shape has sides 5, 4, and 6.4.

To make Copy 1, multiply each side by the scale factor of 2.

The new sides are 10, 8, and 12.8.

Review
scale factor

For example, the original shape has sides 5, 4, and 6.4.

To make Copy 2, multiply each side by the scale factor of 0.5.

The new sides are 2.5, 2, and 3.2.

Review
scale factor

Multiple Select

What does scale factor mean?

• the number you multiply by to create a new shape

• the size of the angles

• the sum of all the side lengths

Match

Look at triangle B. Multiply each side times 2. Answer the questions below.

• What is the original triangle?

• What is the new triangle?

• How did we make the new triangle?

• What is the scale factor?

B

E

Multiply each side times 2.

2

• B

• E

• Multiply each side times 2.

• 2

Match

Mr. Wolfe drew a triangle. Then he multiplied each side times four. Now answer the questions below.

• One side is 4. 4x4 =

• One side is 5. 5x4 =

• One side is 6. 6x4=

• What is the scale factor?

16

20

24

4

• 16

• 20

• 24

• 4

In math, we use numbers to tell a story.
We use tables and graphs to show something that happens in real life.

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Review comparing data

Match

We use the slope to tell a story. The story of this slope is "miles traveled" per "hour." The slope is "miles" divided by "hours."

• How many miles in 3 hours?

• How many hours to travel 120 miles?

• How many miles in 1 hour?

• What is the slope? $$\frac{miles}{hour}$$

180 miles

2 hours

60 miles

• 180 miles

• 2 hours

• 60 miles

• $$\frac{60\ miles}{1\ hour}=\ 60$$

Match

We can also use a table to tell a story. The story of this table is "dollar cost" per day. Answer the questions below.

• How much does it cost for 3 days?

• How many days do you receive for $92.50?

• What is the price for 4 days?

• If you pay $111.00, how many days is that?

$55.50

5 days

$74.00

6 days

• $55.50

• 5 days

• $74.00

• 6 days

Multiple Choice

Using a table, we can find the cost for one day using division.

This is the slope. Choose the correct formula and slope.

$$\frac{dollars}{days}$$

• $$\frac{\text{}55.50}{3}=\text{}18.50$$

• $$\frac{3}{55.50}=\ 0.05$$

• $$74.50-55.50=19$$

Sometimes you have two points on a line. Look at the green dots.

(-6, 4) and (2, 1)

​

Review
use the equation to find slope

How do you find the slope?
do it on your calculator :)

(-6, 4) and (2, 1)

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But wait!
those are the same numbers as the triangle!

(-6, 4) and (2, 1)

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Let's try it one more way...

Multiple Choice

What is the slope of the line?

Remember: rise/run

• $$-\frac{3}{8}$$

• $$\frac{3}{8}$$

• $$3$$

• $$\frac{8}{3}$$

Is a slope positive, negative, or zero?

How to tell...

Review type of slope

Multiple Select

A flat road has no slope at all. It is not steep at all. It is flat. We say it has zero slope. Choose the lines below that have zero slope.

Multiple Select

A cliff jumper is someone who jumps off of a cliff into the water. The cliff is straight up and down. It is not steep or flat. We say the slope of a cliff is undefined. Lines that are straight up and down have an undefined slope. Find the lines with undefined slope.

Multiple Choice

Look at the bird. It is skiing "downhill."

When the line is higher at the left and lower at the right, we say it is a negative slope. Find the other line with negative slope.

Multiple Choice

Look at the motorcycle. It is driving uphill. When the line is lower on the left and higher on the right, we say it has a positive slope. What line below also has a positive slope?

You did it! Now you will do amazing on the test!