Variation
Constant of variation
The fixed number k linking the quantities in a variation relationship.
| English | Constant of variation |
|---|---|
| Bahasa Melayu | Pemalar variasi |
| 中文 | 变化常数 |
How it is used
In y = kx with y = 20 when x = 4, the constant of variation is k = 20 ÷ 4 = 5, so y = 5x. In y = k/x with y = 20 when x = 4, k = 20 × 4 = 80.
Where it shows up in SPM
The constant of variation k appears in every question of the Form 5 Variation chapter. In Paper 1 you find k directly; in Paper 2 finding k is the first step, then you reuse the same k to predict later values.
Don't confuse it with
Frequently asked questions
Is k always found the same way?
No. It depends on the model.
For direct variation y = kx you divide (k = y ÷ x); for inverse variation y = k/x you multiply (k = xy); for joint variation you substitute all values and solve. Always write the model first.
Does k change between parts of the same question?
No. Once you find k from the first set of values, it is fixed for the whole question.
You reuse the same k with the new numbers in every later part. A changing k usually means an arithmetic slip.
Can k be a fraction or decimal?
Yes. If y = 6 when x = 8 in direct variation, k = 6 ÷ 8 = 0.75, so y = 0.75x.
Keep it as an exact fraction like 3/4 where possible to avoid rounding errors in later parts.