In what form is an equation that relates two proportional quantities x and y? A.

y=k+x, where k is the constant of proportionality
B.

y=kx, where k is the constant of proportionality
C.

y=kx, where k is the constant of proportionality
D.

y=xk, where y is the constant of proportionality

Step-by-step explanation: The constant of proportionality k is given by k=y/x where y and x are two quantities that are directly proportional to each other. Once you know the constant of proportionality you can find an equation representing the directly proportional relationship between x and y, namely y=kx, with your specific k.