This entire lesson is centered on investing money. Sometimes we take it for granted that eight grade students understand what it means to invest money, but many do not. Open today with a video clip such as the one I linked to Brewster’s Millions. It would be an interesting way to begin discussing investing versus spending money because in the movie Brewster must spend $30 million dollars in one month in order to inherit $300 million in full. Students would be hooked discussing methods of spending money and you could lead the discussion about which ideas would actually be investing and against the rules of the movie.
Clarify your learning goals for the activity today by asking students to take one minute to read the investment ad from the local newspaper. I will include two versions of the activity today, PDF and Microsoft Word file. I personalized the activity to my town and my principal. I highly recommend personalizing the activity to your community and school. After students read independently, take about one to two minutes to brainstorm allow what the ad is really saying about the investment. Discuss when the money is doubled versus when the $100 service fee is deducted. Clarify that today student’s will be working with investments and trying to grow or increase your initial amount.
Allow students about 10 minutes to work on questions one and two in cooperative groups. Students will struggle with question two because the initial investment was a decimal quantity. Some students will begin to productively work backwards but most will rely on guess and check. This is a great way to learn that guess and check better not be your only strategy for solving math questions. Allow students time to work and finally realize for themselves that the initial amount is not a whole number. As students are working, walk about the room note different approaches to answering question two and providing feedback to help students move productively towards answering question two. As you see different approaches that are eventually helping students to a correct answer, ask each group to present their thinking during the mini-wrap up over these first two questions. During the wrap up, either ask students to script their work on the board and explain their thinking to the class, or allow students to place their papers under the document camera if the work was so extensive that it would take five to ten minutes just to copy over onto the board. Discuss as a whole class which approach is correct if all groups found the same initial investment. Then discuss which approach arrived at the initial invest faster, more efficiently than the others. You will always have guess and check students but hopefully you will also have some thinking algebraically students who work backwards in a structured pattern.
After a full mini-wrap up students should be willing to learn strategies for working productively to answer similar questions and leave guess and check behind. Allow students time to work collaboratively to complete questions three through six. Hold a short mini-wrap up of these answers before students complete the table in questions seven. If students have incorrect answers to questions three through six and input these into the table, the goal and focus of question seven is lost.
For the remainder of the class period and then homework if not finished during class, have students work collaboratively to complete questions eight through eleven (up to the extension activity). These types of thinking questions are great for discussion assignments in Edmodo.com. Again, most of my students have Internet and computers at home. Our library is also open each morning for about 20-25 minutes with computers available. So, I like to make Edmodo assignments when possible. I would tell students that certain questions from the homework will be posted as discussion assignments in Edmodo tonight and it is their homework assignment to not only complete on paper through question eleven, but also to post at least one comment to every question posted to Edmodo. Replies to other students in Edmodo are also welcome. Then I suggest posting for discussion questions 8 and 11 at least but also question 9 would be a great third option. You can use these posts on your projector board tomorrow to begin a whole class discussion. Overnight, read your students’ responses in Edmodo and assign a badge to your favorite responses so students gain a sense of pride and you can easily locate the best work to use during the lesson opener tomorrow.