Grade 6 · Math · Lesson 9

Write and Interpret Ratios

A ratio is a way to compare two quantities by how many of one there are for each amount of the other. Ratios show up in recipes (3 cups flour to 2 cups water — about 720 mL to 480 mL), sports (15 wins to 5 losses), maps (1 cm represents 50 km), and money (2 dollars per 5 candies). The order of the two quantities matters — a 3:5 ratio is not the same comparison as 5:3.

What this lesson teaches

1Write a ratio comparing two quantities in three notations: a:b, a to b, and a/b
2Simplify a ratio to lowest terms by dividing both terms by their greatest common factor
3Generate equivalent ratios by multiplying or dividing both terms by the same nonzero number
4Distinguish part-to-part ratios from part-to-whole ratios in everyday situations

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