Write V(r, h) for the volume of the cone to emphasize that it is a function of both radius r and height h. The volume of the old cone is V(20, 4) = 1675.52cm3 and the volume of the new cone is V(19.95, 4.05) = 1687.99cm3 . The change of volume is thus
Therefore the approximate volume of the new cone is
l(19.95, 4.05) = 1675.52 − 167.55 · 0.05 + 418.88 · 0.05 = 1688.09 .
The approximate change of volume is thus
l(19.95, 4.05) − V(20, 4) = 12.57 .