Классы

program Project1;

{$APPTYPE CONSOLE}

uses
  math;

type
  //DbВиртуальный класс "объем"
  TCustomVolume = class
  public
    function GetVolume : real; virtual; abstract;
  end;

  //Параллелепипед
  TParallelepipedVolume = class(TCustomVolume)
  public
    X, Y, Z : Real;
    function GetVolume : real; override;
  end;

  //Пирамида
  TPyramidVolume = class(TCustomVolume)
  public
    X, Y, H : Real;
    function GetVolume : real; override;
  end;

  //тетраэда
  TTetraedaVolume = class(TCustomVolume)
  public
    A : Real;
    function GetVolume : real; override;
  end;

  //Шар
  TSphereVolume = class(TCustomVolume)
  public
    R : Real;
    function GetVolume : real; override;
  end;
{ TParallelepipedVolume }

function TParallelepipedVolume.GetVolume: real;
begin
  Result := x * y * z;
end;

{ TPyramidVolume }

function TPyramidVolume.GetVolume: real;
begin
  Result := x * y * h;
end;

{ TTetraedaVolume }

function TTetraedaVolume.GetVolume: real;
begin
  result :=  (sqrt(2)/12) * Power(a, 3);
end;

{ TSphereVolume }

function TSphereVolume.GetVolume: real;
begin
  Result := 4 * pi * Power(r, 3)/3
end;

begin

end.