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Robert B. Davis Institute for Learning. (1993). Reviewing rod relationships and the candy bar problem, Clip 3 of 6: What is the number name for red when the yellow and light green rod is two? A whole class discussion [video]. Retrieved from

A77A78A79-FRC-CMPRF-CLIP003

In the third clip from this classroom session, during the whole class discussion, Sarah and Audra presented their solution to the class. Audra explained that they called the red rod one fourth when the train of yellow and light green was called one, and that the red rod would be called one and one fourth when that train was called two. Researcher Carolyn Maher asked Audra to explain her other solution. Audra built a model of an orange and green train, and showed that the brown rod equaled the length of the train. She lined up four red rods against the train and explained that the red rod would be called one fourth. Erik then said that he agreed with Audra’s explanation. Brian C. told the class that he disagreed with Audra’s second solution. He and Jacquelyn presented their solution at the overhead. He said that the red rod would be called one half if the train was called two. David then offered an explanation for Brian’s solution; he explained that if the yellow and light green train was called two, the train of four red rods would also be called two. He said that two red rods would then be called one, and separated the red rods into two groups of two. He then removed a red rod from one of the groups and showed that it would be called one half. Then, he worked backwards, saying that if another red rod was added, the two red rods would then be called one, and that all four red rods together would be called two. Upon request by the researcher, he repeated this explanation in a similar fashion. The researcher then asked why some students might think the red rod would be called one half. Jacqueline, at the overhead, explained that if the train was called one rather than two, then the red rods could be called one half. The researcher asked the class to think about what was difficult about the problem. Erik explained that the confusion resulted from forgetting that the train was called two rather than one.

http://hdl.rutgers.edu/1782.1/rucore00000001201.Video.000067422

doi:10.7282/T32F7M3N

The video is protected by copyright. It is available for reviewing and use within the Video Mosaic Collaborative (VMC) portal. Please contact the Robert B. Davis Institute for Learning (RBDIL) for further information about the use of this video.