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Transcript and student work are also available.

Robert B. Davis Institute for Learning. (1993). Continuing to explore fraction comparisons, Clip 7 of 7: Erik and Alan compare two third and three fourths [video]. Retrieved from

A89A90A91-FRC-CMPRF-CLIP007

In the seventh clip, Erik and Alan worked to extend their model using the orange and red train to show fourths and halves. They concluded that three fourths was larger than two thirds by one twelfth. The visitor questioned Erik about his model. She asked Erik how much three twelfths would be equal to. Erik replied that it was equivalent to one fourth. She asked him what he could call four twelfths, and he replied that it was equivalent to one third. Alan and Erik then repeated their justification to the researcher. She encouraged them to find another model that would show the solution to the problem. After much trial and error, they built a model that was twenty-four centimeters in length, using a train of two oranges and one purple rod, four dark green rods, three brown rods, and twelve red rods. They showed the visitor that the difference between the two lengths was again one twelfth. The visitor asked them what would happen if they lined white rods against this larger model. Erik and Alan reasoned that they would be called one twenty-fourths and concluded that two twenty-fourths would make one twelfth. Erik then began to add white rods to the model to show that there were twenty four. As he did that, Alan told researcher Amy Martino that the difference between three quarters and two thirds was one twelfth or two twenty-fourths. After Erik lined up the white rods, he concluded that the difference between the two fractions was one twelfth or two twenty-fourths. He repeated this solution to the visitor soon thereafter, and again after he finished recording his solution.

http://hdl.rutgers.edu/1782.1/rucore00000001201.Video.000067458

doi:10.7282/T39G5KCK

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.