设底半径为 r.高为 h V=πr²h h=V/(πr²)
造价J=40πr²+30πrh=40πr²+30πV/r=40πr²+15πV/r+15πV/r
40πr²×15πV/r×15πV/r=常数
∴当40πr²=15πV/r,即r=(3V/8π)^(1/3)时,造价最低.
此时 锅炉的直径与高的比=2r/h=3/4.
设底半径为 r.高为 h V=πr²h h=V/(πr²)
造价J=40πr²+30πrh=40πr²+30πV/r=40πr²+15πV/r+15πV/r
40πr²×15πV/r×15πV/r=常数
∴当40πr²=15πV/r,即r=(3V/8π)^(1/3)时,造价最低.
此时 锅炉的直径与高的比=2r/h=3/4.