Size of [4; -2; 9]

Step by step

The question

Question: find the size of this matrix.

A matrix is numbers in rows and columns, inside big brackets.

Each number in a matrix is called an entry.

1 Count the rows

Rows go across.

We count them: 1, 2, 3.

There are 3 rows.

2 Count the columns

Columns go down.

We count them: 1.

There is 1 column.

The size is rows by columns: 3 by 1.

Rows come first.

We write it like this, and say 3 by 1.

Careful!

Rows always come first, then columns.

1 by 3 would be a different shape.

3 Check

Let's check.

3 rows of 1 make 3 × 1 = 3 entries.

We count all the entries in the matrix: 3.

So the size is right!

Let's look back.

First: count the rows.

Then: count the columns.

Last: check.