Final answer:
The equation that represents the proportional relationship between x and y is y = k/x.
Step-by-step explanation:
The equation that represents the proportional relationship between x (the number of kilograms) and y (the number of inches) is y = k/x.
In this equation, k represents the constant of proportionality.
For example, if k is 2, then y will be half of x. If x is 4 kilograms, y will be 2 inches.