In this Focus on Math blog entry, Carollee Norris describes how she uses a 100-dot array to develop number sense and mental math skills. As she covers some rows (and later rows and parts of rows) on a projected grid, students learn to identify quickly the number of rows and dots that are visible, as well as how many are hidden (to complete 100). Through practice, children are able to visualize the structure of the array and apply it to mental math and problem solving tasks.


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