Thursday, November 7, 2013

Seely Place Elementary School, New York

An open lesson based on Math in Focus (Book 4A Lesson 3.5)

The anchor task in the book is:
Mr. Benson and Mr. McKenzie have \$4,686 altogether. Mr. Benson’s share is twice as much as Mr. McKenzie’s.

Introduction - Students were asked what could a number such as 4,686 represents.

Development - Problem was presented. Spiky and Curly share \$4,686. Curly has twice as much as Spiky. If this strip of paper represents \$4,686, show the amount that Spiky and Curly get.

In this lesson the students gave four responses.

Method 1 - (length) We used a ruler and found out it is 6 inches long. So 4" for Curly and 2" for Spiky.

Method 2 - (parts) We folded the strip into three parts. Spiky gets 1 part and Curly 2 parts.

Method 3 - (fraction) We divided the strip into thirds. Spiky gets 1 third and Curly, the rest.

Method 4 - (misconception) I divide the strip into 2. Since Curly gets twice as much, he gets two parts.

Several students disagreed and stood up to say why that reasoning is not correct. Generally the sentiments were .... "That means Curly gets 2 and Spiky gets zero! That is not twice!!"