Question 330573: if the cost for materials to make a circular metal disk 3 cm in diameter is $.15, what would be the cost for materials to make a disk of the same thickness but 6 cm in diameter?
would the answer be $.45? Thanks. Answer by Fombitz(13828) (Show Source):
You can put this solution on YOUR website! The assumption is that the cost of materials is based on the area of the disk (since the thickness is equivalent).
, where is total cost, is cost per unit area, is area.
The area of a circle is,
From the first example,
The area for the second disk is,
Since A2 is 4 times as much as A1, then the total cost will be 4 times as much.