Transcript Ratio Versus Rate

December 8, 2011
1) Write your homework in your agenda:
Rabbit worksheet. Do all your work on loose
leaf paper!!
2) Take out your Ratio worksheet and leave it
on your desk.
3) Any yellow sheets from progress reports??
4) Any quizzes or M&M posters????
5) Complete the following Warm-Up…
Warm-Up
Are the following ratios
proportionate?
Find the missing value in
each proportion
1) 24
12

8 16
1)
n 4

5 10
2) 4  20
2)
3 2

9 n
3) 25
3)
6 3

n 7
9
45
5

36 6
What am I Learning Today?
Ratio, Rate, and Unit Rate
How will I show that I learned it?
Compare and contrast ratios and rates.
Express rates in a per unit form, where the
denominator is one.
Determine which form of a rational number is most
appropriate in a given situation.
Questions
What is a rate?
Answers
Ratio that compares two quantities with
different units
Rate is read in a “per unit” format
-Miles per hour
-Words per minute
-$0.50 per ounce
What is unit
rate?
How do I find
unit rate?
When is unit rate
used?
When the comparison is to ONE unit
“How much for one?”
How much divided by how many
-Used for comparison shopping and
finding the better deal
Questions
How do I label
unit rate?
EXAMPLE: The
fastest running bird is
the ostrich. An ostrich
can run 240 miles in 6
hours. How far can an
ostrich run in an hour?
Answers
Both units of measure must be kept as part of the
final answer.
What is its rate?
240 miles
6 hours
What is its unit rate? 40 miles or 40mph
1 hour
Unit Rate Example: Doughnuts
a) 3 for $1.00
$1.00 = $0.3333…
3
about 33 cents each
To find unit rate….
divide the total rate
by total # of items
OR
b) $.45 each
$.45 = $0.45
1
45 cents each
What is the better deal??
Now let's take a look at a problem that
involves finding the best buy.
Is bigger better?
The costs of different sizes of boxes of
cereal are shown.
Which box costs the least per ounce?
Size
Price
12 oz
$2.64
20 oz
$3.80
32 oz
$5.44
48 oz
$8.64
Find the unit price, or the cost per ounce, of each box. Divide
the price by the number of ounces.
12-ounce box
20-ounce box
32-ounce box
48-ounce box
$2.64  12 ounces = $0.22 per ounce
$3.80  20 ounces = $0.19 per ounce
$5.44  32 ounces = $0.17 per ounce
$8.64  48 ounces = $0.18 per ounce
The 32-ounce box costs the least per ounce.
Now let's take a look at a problem that
involves unit price and total cost.
 "A sign in a store says: 3 Pens for $2.70. How
much would 10 pens cost?" To solve the problem,
find the unit price of the pens, then multiply by 10.
2.70 = x
3
1
2.70 = 3x
$2.70 ÷ 3 = $0.90
$0.90 x 10 = $9.00
 Finding the cost of one unit first makes it easy to
find the total cost of multiple units.
RATIO
- Compares
similar units
-Read it using
the word “to”
both
- Written as
fractions
RATE
- Compares
different units
- Read it using
the word “per”
-Comparison
-Allows you to
-Can be written
of two
calculate the
3 different ways quantities
“better deal”
-Written with two
-Written as a
numbers
single number
Student Summary
Spotlight
10
K
I
rate
A ratio that compares
two quantities measured
in different units
unit rate
A rate in which the
second quantity in the
comparison is ONE unit
M
90 miles
3 gallons
30 miles/gallon
Holiday Shopping Challenge:
Unit Rate & Total Cost
What’s the better buy?
How much do I owe?
1) Put name and title on your
paper.
2) Number your paper from 1-4.
3) Choose the BEST BUY—the
one with the lowest unit
rate… Not the lowest
TOTAL cost.
4) Slide will automatically
transition after 4 minutes!
5) At the end we will tabulate
your score and see who is
the best shopper! Get
Ready….
#1: Present for your little sister
a) 2 Webkinz for $15.50
OR
b) 3 Webkinz for $20.99
Which is the better buy?
#2: Present for your Mom or
Grandma
a) $36.00 for 3.6 oz at Macy’s
OR
b) $17.00 for 1.7 oz at Wal-mart
Where is the better buy?
#3: Present for your BFF
a) 2 board game $15.99
OR
b) 3 board games for $49.99
Which is the better buy?
#4: Goodies for the Entire Family
a) This chest full of candy:
1 chocolate everyday for
a year for $60
OR
b) $24.99 for a 100-count
bag of chocolate
Which is the better buy?