It is a type of variation in which two or more variables vary directly on each other.

What is the initial step in solving joint and combined variation?

Suppose y varies jointly as x and z. If y =180 when z=15 and x = -3, then find y when x = 7 and z = -5

Suppose p varies directly as r, and p and varies inversely as t. If t=20 when p=4 and r=2, then find t when r=10 and p= -5

Translate this variation statement into its variation equation: “In Anthropology, cephalic index is used to estimate the dimensions of the bones. The cephalic index c varies directly as the width w of the head and inversely as the length L of the head when viewed from the top.”

Translate this variation statement into its variation equation: “The appropriate length s of a rectangular beam varies jointly as its width w and its depth d”

Translate this variation statement into its variation equation: “The drag force F on a boat varies jointly with the wet surface area A of the boat and the square of the speed s of the boat.”