Concept:When the radius is fixed, the volume of a cone is directly proportional to its height.Explanation:Let the original radius be r and original height be h.Original volume: V1=31πr2h.When the height is doubled, the new height is 2h.New volume: V2=31πr2(2h)=2(31πr2h)=2V1.Increase in volume: V2−V1=2V1−V1=V1.Percentage increase: V1V1×100%=100%.Answer:The volume will be increased by 100%.