WHAT DO WE CALL A COMPARISON BETWEEN TWO OR MORE QUANTITIES? RATIO We just found the RATIO of boys to girls. Is the ratio of girls to boys the same ? No, when writing a ratio, ORDER matters.
What is a ratio?
IT’S FRIDAY NIGHT AND YOUR FRIENDS ARE HAVING A PARTY……
The ratio of girls to guys is 2 to 12.
Would you want to attend the party?
HOW MANY BASKETBALLS TO FOOTBALLS ARE THERE?
For every 4 basketballs there are 6 footballs.
The ratio is 4 to 6.
WHAT ARE SOME OTHER WAYS WE CAN WRITE THE RATIO OF BASKETBALL TO FOOTBALLS?
4 to 6
4 : 6
First quantity to Second quantity First quantity : Second quantity First quantity divided by the second quantity (as a fraction ). Every ratio can be written in 3 ways: Careful!! Order matters in a ratio. 4 to 6 Is NOT the same as 6 to 4
WRITE THE RATIO OF SANDWICHES TO COKE BOTTLES 3 DIFFERENT WAYS.
6:8 , 6 to 8, and 6
Since a fraction can be simplified, We can simplify the ratio 6/8 to 3/4. The ratio of sandwiches to coke bottles can also be expressed as 3 : 4 or 3 to 4. In other words, ratios can be simplified to form equivalent ratios.
Simplify the following ratios:
4 to 8
10 to 8
8 to 10
Step 1 – Write the ratio as a fraction Step 2 – Simplify the fraction (Find the greatest common factor (GCF) of both numbers and divide the numerator and denominator by the GCF). Step 3 – Write the equivalent ratio in the same form as the question
= 4 / 4 = 1 = 1 to 2
8 8 / 4 2
GCF = 4
EQUIVALENT RATIOS CAN BE FORMED BY MULTIPLYING THE RATIO BY ANY NUMBER.
For example, the ratio 2 : 3 can also be written as
4 : 6 (multiply original ratio by by 2)
6 : 9 (multiply original ratio by by 3)
8 : 12 (multiply original ratio by by 4)
The ratio 2 : 3 can be expressed as
2x to 3x (multiply the original ratio by any number x )
A ratio that compares more than 2 quantities is called a compound ratio.
A cake recipe says the ratio of cups of milk , sugar , and batter are 1 : 2 : 4 .
This means that there is one cup of milk for every two cups of sugar and four cups of batter.
A BAG CONTAINS 18 YELLOW, BLUE, AND RED MARBLES. THE RATIO OF YELLOW TO BLUE TO RED MARBLES IS 4 : 2 : 3 .
Write the ratio of yellow to blue marbles in simplest form.
What is the ratio of yellow to red marbles?
How many yellow marbles are there?
4 : 2 can be simplified to 2 : 1 4 : 3 Yellow : Blue : Red is 4 : 2 : 3 Since any multiple of this is an equivalent ratio, this can also be written as 4x : 2x: 3x Let 4x = yellow, 2x = blue , 3x = red 4x + 2x+ 3x = 18 9x = 18 X= 2 Since the question asks for yellow marbles, there are 4 x or 4 ( 2 ) = 8 yellow marbles.
PRACTICE PROBLEM # 1
It takes Max ¼ of an hour to ride his bike to school, and it takes Riley 21 minutes to walk to school.
Write a ratio comparing Max’s time to Riley’s time.
PRACTICE PROBLEM #2
A TV normally sells for $400 is on sale for $340. The tax on the reduced price is $23.80, so the total cost with tax is $363.80.
What is the discount rate?
What is the tax rate?
Including tax, how much would a customer save by buying the TV on sale?
PRACTICE WORD PROBLEMS
You go to a party where the ratio of boys to girls is 28 to 56. Express the ratio of boys to girls in simplest form.
Explain what this ratio tells us.
28 / 56 = 1 / 2
The ratio of boys to girls is 1 to 2
(2) For every 1 boy there are 2 girls at the party.
PRACTICE WORD PROBLEMS
Mindy has 72 candy bars. If the ratio of Mars to Snickers is 8:4, Find the number of each type of candy.
Explain what this ratio tell us.
Suppose a team has won 15 of it’s first 38 games. How many games must it win in a row to bring its winning percentage to at least .500?