Understand the idea.
Rows go across
An array lines objects up in straight rows and columns. Rows go across, and every row contains the same number. In the picture, count three rows and four dots along each row; both counts are needed to find the total.
Columns go down
Columns go down. The same dots form four columns with three dots in each. Counting by rows or by columns must give the same total, because changing how you describe the arrangement does not add or remove dots.
See the method in action.
Count by rows
How many dots are in the 3-row array?
Worked solution
- 1
Read the array by rows.
Each of the three horizontal rows contains four dots.
- 2
Count two rows, then the last row.
Adding one four for each row counts every dot exactly once.
12 dots.
Make a different array
Arrange 10 counters in 2 equal rows. How many counters are in each row?
Worked solution
- 1
Share the counters between two rows.
Place one counter in each row in turn until all ten have been placed.
- 2
Check that the equal rows use every counter.
Two rows of five have the same length and use the full total.
5 counters per row.
Try it yourself.
Check your understanding
An array has 2 rows of 6. How many objects are there?
Show answer & reasoning
12
Each of the two rows contributes six objects. Adding the rows gives objects.
Keep practising
6 worksheet questions
Read the questions online
- Count the dots in this array.
- How many rows and columns are in this array?
- Draw an array with 2 rows of 3 dots. How many dots?
- There are 4 rows of 5 chairs. How many chairs?
- Arrange 12 counters in 2 equal rows. How many in each?
- An array has 2 rows of 5. If you turn the page, it has 5 rows of 2. Has the total changed? Explain.
Read the worked solutions
- Count the dots in this array.
There are 2 rows of 4: .
8 dots. - How many rows and columns are in this array?
Trace three horizontal rows and two vertical columns.
3 rows and 2 columns. - Draw an array with 2 rows of 3 dots. How many dots?
.
6 dots. - There are 4 rows of 5 chairs. How many chairs?
.
20 chairs. - Arrange 12 counters in 2 equal rows. How many in each?
.
6 counters. - An array has 2 rows of 5. If you turn the page, it has 5 rows of 2. Has the total changed? Explain.
Turning the arrangement does not change the objects.
No. There are still 10 objects.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics
Equal groups; arrays; repeated addition; sharing/grouping; twos facts; doubling and halving.
Official curriculum source ↗