The purpose of this activity is to introduce the game Mystery Quadrilateral and strategically consider the questions that could be asked next to determine a mystery quadrilateral. Students play a round of this game against the teacher. In the next activity, students will play this game in groups of 2.

• “What kinds of questions might help you figure out the mystery quadrilateral?” (Questions about something we didn’t already know about the shape. General questions to narrow down the type of quadrilateral, then more-specific questions to figure out which one.)

The purpose of this activity is for students to practice describing geometric attributes of a quadrilateral with increasing precision by playing a game. Students should be encouraged to ask questions such as, “Are all the sides the same length?” rather than, “Is it a square?” to keep the focus on attributes of the quadrilateral rather than the name. As students decide which questions to ask they think about important attributes such as side lengths and angles and have an opportunity to use language precisely (MP6, MP7).

Students will use the quadrilaterals from the previous lesson to hide in the “mystery quadrilateral” folder, but will have a copy of all the shapes in their student book to support them in asking questions to narrow down the shape. Students can also cover shapes in their student book with counters as they rule out shapes.

• “What shapes were the easiest to figure out and why?” (W was easy because it was so different with one angle pointing in. X was easy because it was the only square resting on a side.)
• “What shapes were the most challenging to ask questions about and why?” (FF was challenging because none of the sides were the same length, and it was hard to get more information with “yes” or “no” questions. M and BB were hard to tell apart because they were so similar and it was hard to figure out what questions to ask.)