Ratios

Lesson 7 – 1

Vocabulary

• Ratio: a comparison of two numbers

(quantities) by division

• Equivalent Ratios: ratios showing the

same relationship between two quantities.

(have the same value)

How to write a ratio?

3 ways!Example: ratio of 5 girls to 3 boys

5 to 3 5:3

Also possible with algebra, a to b

a to b a:b

3 5

b a

Need to Know about Ratios!

# 1: order matters. Follow the order from the question.

# 2: label your work. This will help when you set up proportions.

# 3: write the ratio in simplest form!

# 4: DON’T change to mixed numbers. It is ok to have improper fractions when writing a ratio.

Practice writing ratios

In the SMS choir, there are 24 sopranos, 2 tenors, 4 basses, and 15 altos. Find each ratio.

# 1: What is the ratio of tenors to sopranos?

# 2: What is the ratio of altos to members in the choir?

# 3: What is the ratio of sopranos to altos?

12 1

3 1

5 8

Rates

Lesson 7 – 2

Vocabulary

• Rate: a ratio that compares two

quantities measured in different units

• Unit Rate: a rate simplified to a

denominator of 1 unit.

• Example: I can type 200 words in 4 minutes

My Rate = Unit Rate = 4 minutes200 words

1 minute50 words

‘per’ means to ‘divide by’

Example: miles per hour means to divide number of miles by number of hours. So, if you drive 360 miles in 8 hours, and you want miles per hour, then:

Answer: 45 miles per hour or 45 mph

360 miles8 hours

Find the Better Buy!

Find the unit rate to determine the better buy.

# 1: 5 pairs of socks for $4.95

8 pairs of socks for $7.95

# 2: 4 CDs for $60

6 CDs for $75

5 CDs for $70

3 CDs for $40

5 pairs for $.99 per pair

6 CDs for $12.50/ CD

$13.33/CD

$14.00/CD

$12.50/CD$15.00/CD

$0.994/pair

$0.99/pair