Lesson 1: Understand Ratios6.AT.1

I can…

I can write and describe a ratio that compares two quantities.

Key words

• Understand Ratios — A ratio compares two things.
• Ratio — A way to compare two amounts, like 3 to 2.
• Comparison — Looking at two amounts to see how they relate.
• Part-to-part — Compares one piece of a group with another piece.
• Part-to-whole — Compares one piece with the whole group.
• Colon notation — Write a ratio with two dots between the numbers, like 3:2.
• Tape diagram — A bar cut into equal parts to show amounts.
• Double number line — Two number lines side by side. Marks that line up go together.
• Term — One of the two numbers in a ratio.
• Simplest form — A ratio with the smallest whole numbers that still match.
• Total parts — Add the two parts of a ratio.

Steps

1. Chef Reyes uses 3 cups of apple juice for every 2 cups of sparkling water.
2. I am comparing two amounts: apple juice and sparkling water.
3. I write apple juice to sparkling water, in that order, as 3 to 2, or 3:2.
4. I can also draw the ratio. On a tape diagram I give apple juice 3 equal parts and sparkling water 2 equal parts, so one batch is 5 parts in all.
5. Those same 5 parts show a second ratio: apple juice to the whole fruit drink is 3 to 5.
6. On a double number line I line the two amounts up: 5 cups of fruit drink pairs with 3 cups of apple juice, and 10 cups of fruit drink pairs with 6 cups of apple juice.

Try it

A garden has 7 tulips and 4 daisies. What is the ratio of daisies to all the flowers in the garden?

Check your answer

4:11

Total flowers = 7 + 4 = 11. The ratio of daisies to all the flowers is 4:11.

Sentence starter

I know ___ because ___.

Goal: I can explain a comparison using the words ratio, part-to-part, part-to-whole, and colon notation.