SECTION 4.2 WHAT ARE RATES?UNIT RATES
I) WHAT ARE RATES:
A comparison of two quantities measured in “different”units
Ie: Speed: meters per second, km/hour, miles/hour
Speed of light 300,000km/s
Wages and Salaries
MacDonalds: $8.25/hr
Accountant (CGA): $50/hr
Doctor: $200/hr
Cost
Groceries
Corn: 3 corn/$1
II) UNIT RATES
When finding unit rates, the second quantity has a unitof “one”
Useful for comparing prices and rates
Divide both values by the number in the denominator
RATE:
Conversion RATE (Unit Rate)
$1.00 / 3 corn
200m / 20seconds
25 clicks in 30seconds
$0.33 / 1 corn
10m / 1 second
0.8333 clicks / 1 second
Divide $1by 3
Divide 200mby 20
Divide 25mby 30
EX: TOM WENT TO COSTCO, SAFEWAY, AND SUPERSTORETO BUY MILK. HE GOT THE FOLLOWING PRICES FOR EACHPRODUCT. WHAT IS THE UNIT RATE FOR EACH ONE?WHICH ONE SHOULD HE BUY?
Unit Price:
Unit Price:
Unit Price:
The $5.59/4L at Costco is the best buy
Costco
Safeway
Superstore
III) COMPARING UNIT PRICE
Learning how to find unit pricing will help you save money
Once you have two items priced out per unit you canproperly compare which one is cheaper
Ex: If peanut butter is sold at $6.99 for a 1.5 kg jar and at$2.50 for a 200 g jar which is the better buy?
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1st Option
2nd Option
The 1st option is cheaper (Buy in bulk)
Practice: Which is a better deal? 5 CD’s for $12.99 or 1CD for $2.99? Use unit pricing.
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1st Option
This is cheaper thanbuying 1 cd at a time
Practice: A store sells juice at $0.99 for 355 mL and $1.19for 500 mL, which is the better buy?
1st Option
2nd Option
The 2nd option is cheaper (Buy in bulk)
IV) SPEED, TIME, AND DISTANCE (STD):
Some questions on rates involve Speed, Time, andDistance
Ex: If Ivon can run 250m in 20seconds and Yolanda canrun 4 km in 5min, who can run faster?
Ivon’s Speed:
Yolanda’s Speed:
Yolanda’s runs faster!!
Practice: Usain Bolt can run 100m in 9.58seconds. Whatis his speed in meters per seconds?
Practice: The speed of light is 300,000 km/s. If thedistance between the sun and earth is 150,000,000km,then how long does it take light to travel from the sunto the earth?
That’s about8.33 minutes
Finish
Y
X
X
Y
Challenge: Mr Y and Mr. X are racingeach other around a 30km track threetimes. Mr. Y can drive at 120km/hrand Mr. X can drive at 100km/hr.Who will finish the race first and byhow much time?
Find the total distance travelled
Find the time for each driver
To find the time, divide
the distance by the speed
Convert the time tominutes and thensubtract them to get thedifference
