The purpose of this activity is for students to create arrays with counters. Students get sets of 6, 7, and 9 counters. Based on their experiences with images that show an even number of objects arranged in 2 equal groups, students may use 6 counters to make an array with 3 rows and 2 columns or 2 rows and 3 columns. They may wonder if 7 or 9 counters can be arranged in an array since they are not even numbers. Encourage students to experiment with other ways of arranging the counters that include more than 2 rows or columns. Students may also make an array with 1 row. Arrays with 1 row or 1 column will be studied in future grades, so for the rest of this unit, students should be encouraged to make arrays with more than 1 row and more than 1 column.

If students create arrangements with unequal rows or only try to make arrays that have 2 rows or 2 columns (2 equal groups), consider asking:

• “What have you tried so far? How many counters were in each row?”
• “_____ counters in each row did not make an array without any leftovers. What other amount of counters in each row could you try?”

• “7 and 9 are both odd numbers. What did you notice about the arrays you could make with them?” (We couldn’t make an array with 2 rows. With 9 counters, we could do 3 rows with 3 counters in each row. For 7, the only way we did it was with 1 row with all 7 counters.)
• Display student work for array of 6 or arrange counters to show:

• “How can we describe this array of 6 counters?” (There are 3 on the top and 3 on the bottom.)
• “Another way to describe this array is to say there are 2 rows with 3 counters in each row.”

The purpose of this activity is for students to describe the number of rows in an array, the number of objects in each row, and the total number of objects. They use this vocabulary to describe arrays and to create arrays given a number of counters and a number of rows (MP6). They may use trial and error to build these arrays.

This activity uses MLR8 Discussion Supports. Advances: speaking, conversing.

• Display student work for the array with 20 counters.
• “Describe _____’s array.” (It has 20 counters, it has 4 rows and 5 counters in each row.)
• “How can we prove there are 20 counters in this array?” (We can count them. We can skip-count by 5. We can add . The top 2 rows have 10 and the bottom 2 rows have 10, so we can add .)