# Express: y varies directly as x and inversely as the square of z.

We will use the concept of direct and indirect proportion to express the above relation.

## Answer: y = ( k × x ) / z^{2}, where k is the constant of proportionality.

Let us see how we will use the concept of direct and inverse proportion to express the above relation.

**Explanation:**

Direction proportional means that if one variable y increases, then the other variable x increases and if y decreases, then x also decreases.

Mathematically, y ∝ x is the representation of direct proportionality.

Inverse proportional means that if one variable y increases, then the other variable x decreases and if y decreases, then z increases.

Mathematically, y ∝ 1 / z is the representation of inverse proportionality.

Hence, combining the above two equations we get that, y ∝ x / z^{2}

Now, removing the proportionality sign, a constant comes into play and we get that, y = ( k × x ) / z^{2}, where k is the constant of proportionality.