An array is equal groups lined up in rows. Every row has the same number, like seats in a theater or eggs in a carton.
Why it works
Each row is a group, and every row is the same size. So an array with 4 rows of 6 is 4 groups of 6, which is $4 \times 6$. You can count by rows instead of by dots: 6, 12, 18, 24.
Key idea
An array with $r$ rows and $c$ in each row shows $r \times c$. Rows go across; columns go up and down.
Worked example: Count by rows
How many dots are in an array with 4 rows of 6?
- Each row has 6. There are 4 rows.
- Count by 6s, one count for each row: 6, 12, 18, 24.
- So $4 \times 6 = 24$.
Answer: $24$ dots
Worked example: Seats
A theater has 7 rows with 5 seats in each row. How many seats?
- 7 rows of 5 is $7 \times 5$.
- Count by 5s seven times: 5, 10, 15, 20, 25, 30, 35.
Answer: $35$ seats
Common mistake
Counting every dot one by one. It works for small arrays, but it is slow and easy to lose your place. Find the size of one row, then count by that number once for each row.