According to the fifth grade common core standards students should be able to multiply multi-digit numbers using the standard algorithm. There have been other strategies, used to develop student understanding, taught in previous grades such as partial products and lattice but now it is time to move to the more efficient standard algorithm.
In today’s lesson, I hope to show students the efficiency of the standard algorithm and introduce the turtlehead method to them. I want them to focus on explaining their thinking as they are completing each problem.
To begin this lesson I will invite students to compete against me in completing a multiplication problem. I will have the student use lattice multiplication while I use the standard algorithm.
Alright, we’re going to start out today with a little competition. In order to find a worthy opponent I need someone who uses lattice to solve multiplication problems. Is there anyone who feels brave enough to come up to the board and do a multiplication problem racing against me?
I get several students to volunteer so I call a few up and give them the problem. 72 x 14. We all write the problem down and get ready to begin. I say start and we’re off! While the students are still completing the drawing of the lattice box I announce that I’m done. In a joking manner I banter with the students.
I’ll just wait until you’re done. What took you so long? (Waiting for few puzzled responses.) Did you guys not hear me say start? (Students smiling and lightly laughing.) To the rest of the class: What happened here?
I ask the students to return to their seats and I have everyone turn to their neighbor and talk about what happened during the competition. I bring students back to the whole group to discuss. Students quickly make the connection that my method was much quicker because I didn’t have to draw the lattice first.
Today I’m going to show you the steps for this type of multiplication called the standard algorithm. Some of you might already be familiar with this type of multiplication but you may not have learned it using the turtlehead method.
To introduce the turtlehead method of multiplication I show the students a short video clip using the method. When the video is finished I ask students to summarize the steps in the video.
We then do some sample problems together using the document camera. After two problems, I place another on the whiteboard and ask for a volunteer to walk us through the problem using the turtlehead method. For this first student walk through I choose a student that I know will be able to explain the problem very well. I write one more problem on the board and choose a student that I know is probably struggling a bit with the process. I have this student come up to the board and begin the problem. If they struggle, I allow them to call on another student to give them some advice as to what to do next. I cheer the struggling student for hanging in there, and assure them that they are not the only one struggling. We are all just getting started with something new!
To offer students some additional practice with the turtlehead method I give them a set of six two-digit multiplication problems to work on with a partner. While students are working with their partner I ask them to focus on explaining the problem step by step to one another.
I circulate and listen in. If students are struggling, I judge whether it is productive struggle, or "in the deep end" struggle. If students are moving toward frustration, I'll suggest some resources (in this case, they can watch the video again) that they can turn to. I'm trying to create independent learners, and encouraging students in identifying and using resources lays a foundation for their future success.
After allowing students time to work I bring the class back and ask students to share out their thinking of how they solved each problem.