Matrices
Order of a matrix
The number of rows by the number of columns, e.g. a 2×3 matrix.
| English | Order of a matrix |
|---|---|
| Bahasa Melayu | Peringkat matriks |
| 中文 | 矩阵的阶 |
How it is used
The matrix (1 2 3; 4 5 6) has 2 rows and 3 columns, so its order is 2×3. To multiply two matrices, the columns of the first must equal the rows of the second: a 2×3 times a 3×1 is allowed and gives a 2×1 result.
Where it shows up in SPM
Early in the Matrices chapter (Form 5). Paper 1 asks you to state a matrix's order, or to decide whether an addition or multiplication is possible; the order rule decides both.
Don't confuse it with
Frequently asked questions
Is a 2×3 matrix the same as a 3×2 matrix?
No. A 2×3 has 2 rows and 3 columns, while a 3×2 has 3 rows and 2 columns, so they are different shapes.
Order is always written rows first, then columns, and swapping the two describes a different matrix.
How does order tell me if I can multiply two matrices?
Multiplication works only when the number of columns of the first matrix equals the number of rows of the second. So a 2×3 times a 3×2 is allowed, and the answer takes the outer numbers, giving a 2×2 matrix.
If they do not match, the product is undefined.