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I was just looking at standard 2.OA.4 (use addition to find the total number of objects arranged in rectangular arrays with up to 5 rows and up to 5 columns…) and I was wondering, does this mean we should not have children build or work with arrays for numbers such as 14, 18, and 21? Since in order to build such arrays, either the rows or the columns need to be larger than 5. For example, the only way to build an array for 14 is 2 rows and 7 columns or 7 rows and 2 columns.
Or, are students not to be building the arrays and are just to write the repeated addition equation for given arrays (with up to 5 rows and 5 columns) to express the total. Can you please clarify?
Thanks!
Recycling Bill’s earlier answers to questions of a similar nature (http://commoncoretools.me/2011/12/26/progression-for-statistics-and-probability-grades-6-8/#comment-2135):
“that which is not mentioned in the standards is not thereby forbidden”
“that which is mentioned in the progressions is not thereby required.”
However, a main focus is for students in grade 2 is get fluent with addition within 20 (2.OA.2), so it doesn’t seem as work with arrays that have more than 5 rows or columns is much of a priority in grade 2. It may help to compare grades 2 and 3 of the Operations and Algebraic Thinking Progression which is here: http://ime.math.arizona.edu/progressions/. That has a lot of discussion of the subtleties of arrays in the grade 3 section.
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