Math - Combining Sets

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Watch these two boys count small sets of blocks and then combine them to double the count. Would an older pair of children have to start at "one" each time they wanted to know the total number of blocks? Are there other places where the boys could have used the logic of number sets to get the total count, such as one less or for that matter, sets so small you "know" the size of the set? We might wonder why they jumped from saying "nine" to saying "eleven" instead of "ten." Notice another stumble on saying "eight" instead of "six" immediately after having a total set of eight to count. Sometimes recent memory for the last set counted interferes with saying the correct number for a revised set. What patterns do you notice in their play with combining and separating the counters? Note: The downloaded folder will include a more detailed analysis of the video clip. Keywords: Fours, Math, Child-Child, Blocks, Counting, Sets, Logic Length of video: 4 minutes 17 seconds