In this question, the student gives a different total for the sum of the repeated addition and the total number of spoons in the group. This indicates that the student might not understand that the sum of the repeated addition equation needs to represent the total number of objects. Although the student made a mistake in finding the sum of 8 + 12, if the student understood the meaning of the repeated addition equation, the student may have caught the computation error.
1. Support Materials
Although the answer key matches the prompt by representing each problem with a tape diagram, 2.OA.C.4 does not require that representation of repeated addition. For 2a and 2b, the student finds the correct total without using the tape diagram model. It would be interesting to know whether the student chose not to use the tape diagram because the student did not feel the need for it or because the student did not, or could not, read the prompt.
2.OA.C.4: Use addition to find the total number of objects arranged in rectangular arrays with up to 5 rows and up to 5 columns, write an equation to express the total as a sum of equal addends.
The student draws pictures for c and d, where the equal groups are represented with words rather than equations. These pictures are accurate representations of the equal groups described, and the repeated addition equations are correct. It is possible that the student needed the visual model in order to write the addition equation and find the sum or that the student does not understand what a tape diagram is.