Ratios

Ratios

Ratios

We're ending our scales unit by applying the concept to ratios.

Ratios is a type of scaling that compares two or more values by using a colon symbol.

Cookie Recipe

One batch (12 cookies) is made with 3 flour to 2 butter to 1 sugar. When we write ratios, they are written in the order that is given.

Multiple Choice

If one batch requires 3 cups flour, 2 cups butter, and 1 cup sugar, what would the ratio written out look like?

• 1 : 2 : 3

• 2 : 1 : 3

• 3 : 1 : 2

• 3 : 2 : 1

Multiple Choice

If one batch requires 2 cups butter, 1 cup sugar, and 3 cups flour, what would the ratio written out look like?

• 1 : 2 : 3

• 2 : 1 : 3

• 3 : 1 : 2

• 3 : 2 : 1

A non-food example: The ratio of teacher to student is about 3 to 15 or 3 : 15.

Multiple Choice

The ratio of teacher to student is about 3 to 15 or 3 : 15. The number 15 represents what?

• The number of students

• The number of teachers

Multiple Choice

Let' simplify (find the smallest equivalent ratio) for the number of teacher to student ratio. It is currently 3 : 15, but what can we simplify it to?

• We can't. It's 3 : 15

• 1 : 5

• 2 : 20

• 3 : 25

So for every 1 teacher, there are 5 student.

Ratios act just like fractions.

Cookie Recipe

Just like with scales and fractions, when we affect one value, the other values are affected too.

Multiple Choice

If one batch of cookies require 3 cups flour, how many cups are required for four batches?

• 3

• 6

• 9

• 12

Multiple Choice

The ratio of teacher to student is about 3 to 15 or 3 : 15. If there are 9 teachers, how many students would there be?

• 40

• 45

• 50

• 55

Scaling Down Ratios

Just as easily as we can scale UP ratios by multiplication, we can scale DOWN ratios by dividing.

I don't want to eat 12 cookies. Those are too many cookies.

Since one batch is 12 cookies, I only want to make 6 cookies. How can I modify my recipe to only bake 6 cookies?

We are going to halve the recipe (cut the recipe in half).

The original recipe was 3 cups of flour, 2 cups of butter, and 1 cup of sugar.

Let's do the math.

Let's make it complicated!

Our next field trip is to a grocery store.

Price per _____

Using ratios can help you determine which size of foods is actually cheaper.

Let's buy some grains

If 1 lb of rice is $5.00, but 5 lb of rice is $20.00, which one is the cheaper price per pound?

Multiple Choice

If 1 lb of rice is $5.00, but 5 lb of rice is $20.00, which one is the cheaper price per pound?

• The 1 pound bag

• The 5 pound bag