standard_description: Derive the formula A = 1/2 ab sin(C) for the area of a triangle by drawing an auxiliary line from a vertex perpendicular to the opposite side.
problem_activity: Narrative
The purpose of this activity is for students to make sense of a questionless Put Together/Take Apart, Both Addends Unknown story problem. In this activity, students are asked to show what Lin’s apples could have looked like. The focus of this activity is for students to show the two groups of apples, rather than on answering specific questions about how many red apples and how many yellow apples Lin had. While students may notice that there is more than one possible solution to the story problem, that is not highlighted until the next lesson.
When students explain to a partner how they have represented the apples they reason abstractly and quantitatively (MP2).
MLR8 Discussion Supports.
Use multimodal examples to show the meaning of “some of” and “the rest of.” Use verbal descriptions along with gestures, drawings, or concrete objects to show the groupings.
Advances: Listening, Representing
Required Materials
Materials to Gather
Connecting cubes
Two-color counters
Launch
Groups of 2
Give students access to connecting cubes and two-color counters.
Read and display the task statement.
“Tell your partner what happened in the story.”
30 seconds: quiet think time
1 minute: partner discussion
Monitor for students who accurately retell the story. Choose at least one student to share with the class.
“Use objects or drawings to show what Lin’s apples could look like.”
Activity
3 minutes: independent work time
“Share how you showed Lin’s apples with your partner. Tell your partner how your objects or drawings show Lin’s apples.”
30 seconds: quiet think time
2 minutes: partner discussion
Monitor for students who use two-color counters to show 8 apples, some red and some yellow. Monitor for students who show different decompositions of 8, such as 5 and 3 and 4 and 4.
Student Facing
Lin picked 8 apples at the orchard.
Some of the apples were yellow.
The rest of the apples were red.
Student Response
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Activity Synthesis
Invite previously selected students to share.
As each student shares, ask:
“How many apples did Lin pick?”
“Where do you see the red apples that Lin picked?”
“Where do you see the yellow apples that Lin picked?”
“_____ used red and yellow counters to show Lin’s apples. What could I do if I wanted to draw a picture to show Lin’s apples?” (You could draw 4 red apples and 4 yellow apples. You could draw some circles. You could write r for red and y for yellow.)


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