What a Ratio Says

A comparison between two amounts.

8 problems · about 16 minutes · 6.RP.A.1

What this lesson teaches

The child describes a ratio relationship using ratio language and reads a ratio from a situation.

A ratio compares two amounts.
It can be written 3 to 2, 3 : 2, or 3/2.
The order matters, and part-to-whole is a different comparison from part-to-part.

Straightforward practice. Get the method working first.

4 problems

6 pens and 9 pencils. Pens to total: what is the second number?
Answer 15
Why 6 : 15.
What does a ratio do?
Answer Compares two amounts.
Why A ratio is a comparison.
4 cats and 6 dogs. Cats to total: what is the second number?
Answer 10
Why 4 + 6.
9 boys and 11 girls. Girls to boys: what is the first number?
Answer 11
Why Girls are named first.

The same ideas with more to keep track of.

2 problems

Is 3 : 5 the same ratio as 5 : 3?
Answer No. The order changes what it says.
Why Which quantity is named first?
2 red and 8 blue. Red to total: what is the second number?
Answer 10
Why 2 + 8.

Mixed problems. Work out what kind of question it is before you start.

2 problems

The Fruit Bowl: 5 apples and 7 oranges. What is the second number in the apples to oranges ratio?
Answer 7
Why 5 : 7.
The Whole Bowl: 5 apples and 7 oranges. What is the second number in the apples to total ratio?
Answer 12
Why 5 : 12.