3
Rows in an array
Discover Mathematics P2: Term 2, Lessons 71–80
GoalDescribe an array by its rows and find the total by adding equal rows.
New words
array · objects in equal rows and equal columnsrow · a line of objects going acrossequal · the same amount
Explanation
An array is a neat arrangement of objects in rows. A row goes across, from side to side. In an array every row has the same number of objects. Count how many rows there are and how many objects are in each row. This array has 3 rows of 4 stars. To find the total, use repeated addition: 4 + 4 + 4 = 12. An egg tray, a chocolate bar and the windows of a building are arrays you can see every day.
Worked examples
3 rows of 4 stars. Add the rows: 4 + 4 + 4 = 12. There are 12 stars.
2 rows of 5 apples. 5 + 5 = 10 apples.
4 rows of 3 flowers. 3 + 3 + 3 + 3 = 12 flowers.
Class activity
Array hunt. Find arrays at home: an egg box, a tray of ice cubes, a tile floor, a keyboard. For each one count the rows, count the objects in a row, and write the repeated addition.
Practice
1
How many rows are in this array, and how many in each row?
2 rows with 6 in each row.
2
Write the repeated addition for the array above and find the total.
6 + 6 = 12.
3
An egg tray has 2 rows of 6 eggs. How many eggs in all?
6 + 6 = 12 eggs.
4
Draw an array with 3 rows of 2 dots. Write the repeated addition.
2 + 2 + 2 = 6 dots.
5
An array has 5 rows with 2 in each row. What is the total?
2 + 2 + 2 + 2 + 2 = 10.