A pizza parlor charges $10 for a pizza with a diameter of 8-inches. How much should they charge for a pizza with a diameter of 12-inches if the price-per-area is to remain the same?
The ratio 12/8 = 1.5. If each length increases by a ratio of 1.5, this means that area increases by (1.5)(1.5) = 2.25
The 12-in pizza has more than double the area of the 8-in pizza. To keep the same ratio, the price should be multiplied by 2.25, the same ratio as that by which the area was multiplied.
$10(2.25) = $22.50