Khá "ngắn":

uses crt;
var a:array[1..100000] of longint;
    d,demle,demchan,n,i,k,tong,tich,tongle,tongchan,tichle,tichchan:longint;
    tbc:real;
begin
clrscr;
write('Nhap do dai cua day: ');readln(n);
for i:=1 to n do
  begin
  write('a[',i,']=');readln(a[i]);
  end;
//a
tong:=0; tich:=1;
for i:=1 to n do
  begin
  tong:=tong+a[i];
  tich:=tich*a[i];
  end;
writeln('Tong cac phan tu trong day: ',tong);
writeln('Tich cac phan tu trong day: ',tich);
//b
tongle:=0; tongchan:=0; tichle:=1; tichchan:=1;
for i:=1 to n do
  begin
  if a[i] mod 2=0 then
    begin
    tongchan:=tongchan+a[i];
    tichchan:=tichchan*a[i];
    end;
  if a[i] mod 2<>0 then
    begin
    tongle:=tongle+a[i];
    tichle:=tichle*a[i];
    end;
  end;
writeln('Tong cac phan tu le: ',tongle);
writeln('Tong cac phan tu chan: ',tongchan);
writeln('Tich cac phan tu le: ',tichle);
writeln('Tich cac phan tu chan: ',tichchan);
//c
demle:=0; demchan:=0;
for i:=1 to n do
if a[i] mod 2=0 then inc(demchan)
else inc(demle);
writeln('Co ',demle,' phan tu so le');
writeln('Co ',demchan,' phan tu so chan');
//d
tong:=0;
for i:=1 to n do tong:=tong+a[i];
tbc:=tong/n;
writeln('Trung binh cong cac phan tu trong day: ',tbc:0:2);
write('Nhap so nguyen k=');readln(k);
//e
tong:=0;
for i:=1 to n do
if a[i] mod k=0 then
  begin
  inc(d);
  tong:=tong+a[i];
  end;
if d>0 then
  begin
  tbc:=tong/d;
  write('Trung binh cong cac phan tu chia het cho ',k,': ',tbc:0:2)
  end
else write('Trung binh cong cac phan tu chia het cho ',k,': 0');
readln;
end.