   SEARCH HOME Math Central Quandaries & Queries  Question from swathi, a student: A company manufactures aluminum cans. one customer places an order for cans that must be 15 cm high, with a volume of 1200cm cube. a) use the formula V= pie r squared h to determine the radius that the company should use to manufacture these cans b) graph the function that corresponds to 0 = pie r squared h minus V to determine the radius. Hi,

In the formula $V = \pi \; r^2 h$ you know $h = 15$ cm and $V= 1200$ cubic centimeters. Thus you have

$1200 = \pi \; r^2 \times 15.$

For part a) I would divide both sides of the equation by $15 \pi$ and then take the square root.

The equation above can be rewritten as

$0 = \pi \; r^2 \times 15 - 1200$

and hence if you graph the function

$y = \pi \; r^2 \times 15 - 1200$

the graph will cross the r-axis at the value that corresponds to $y = 0.$

I hope this helps,
Penny     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.