Question 1199119
y = kx is the direct variation equation.
the cost of a pizza varies directly as the square of its radius.
the formula becomes y = k * r^2
r is the radius of the pizza
x = r^2
y is the cost of the pizza.
when the radius is 6 inches, the pizza costs 180.
formula becomes 180 = k * 6^2 = k * 36
solve for k to get k = 180 / 36 = 5.
k always stays the same in that equation.
when the pizza radius is 11 inches, the formula becomes:
y = 5 * 11^2 = 605.
that's the cost of the pizza with 11 inch radius.