This formative is by Kelly Quinn! Below, she describes how each 6th grade Common Core standard is assessed in it so you can see how it fits into what you are already teaching!
CCSS.MATH.CONTENT.6.RP.A.2
Understand the concept of a unit rate a/b associated with a ratio a:b with b ≠ 0, and use rate language in the context of a ratio relationship.
Students are given a ratio about cookies on plates and are asked to find the unit rate. Students are then given a question where they have to find a unit rate of chocolate chips per cookie.