Question

The cost of a pizza varies directly as the square of its radius. If a pizza with a 6-inch radius costs ₱148.00, how much should a pizza with an 11-inch radius cost?

Answer 1

cost = k r^2
when r = 6, cost = 148
148 = k(36)
k = 37/9
cost = (37/9) r^2
so when r = 11
cost = (37/9)(121) = 497.44

or

cost1/cost2 = r1^2/r2^2
148/cost2 = 36/121
36cost2 = 148(121)
cost = 148(121)/36 = 497.44