A relationship where two quantities vary directly from each other is known as ‘Proportional Relationship’. For instance, the variable y varies directly from a variable x. So, y = kx where, k is the constant of proportionality. This signifies that, as x increases, y increases. Likewise, as y decreases, x decreases. Hence, the ratio between x and y always remains the same. The proportional relationship plays a significant role in real life too.