Math CentralQuandaries & Queries


Question from Rosalynn, a parent:

what multiplication fact can be found by using the arrays for 2x9 and 5x9

Hi Rosalynn,

An array is a rectangular arrangement of objects. In describing an array we name the number of rows first followed by the number of columns. In my diagram I have drawn a 2 by 9 array of squares.


The number of squares in the array is $2 \times 9 = 18.$ From the diagram you can also see that $9 \times 2 = 18.$ Maybe the teacher wants to see both multiplication facts, I am not sure.

One of the reason for these questions is to connect multiplication to area. If each square is 1 inch by 1 inch then the area of the array (rectangle) is $2 \times 9 = 18$ square inches. An array however doesn't have to consist of squares. See for example my answer to an earlier question.

What multiplication fact(s?) can be found in a 5 by 9 array?


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