This lesson is focused on the grade-level standard. The teacher makes an explicit connection to prior learning by stating that, previously, students found percent of a quantity using part divided by the whole.  The activity in this lesson is intentionally targeting conceptual understanding. The students are asked to create diagrams that help illustrate percent of increase or decrease.  The teacher makes the mathematics of the lesson explicit by using explanations, representations, and/or examples.  The structured note taker was a unique way for students to illustrate percent of change.  

In this part of the lesson, the teacher is using arrays to model the concept of percent of change.  The model helps the student to see the amount of the original shape and how much it has changed when squares are added or taken away.  

In this part of the lesson, students are prompted by the teacher to explain their thinking and to discuss the reasoning behind it.

The teacher deliberately checks for understanding for two partners who originally thought the answer was 50%.  She asks one group to explain it to her. Students clearly indicate with their explanation that they understand. 

Here, the teacher asks this student to explain and to justify his mathematical reasoning.  She provides specific feedback to help him revise his original work.  
She references the previous problem which was 100% because it was double and asks him if his answer of 70% was reasonable.  "Think about it and see if you can come up with a different answer."