Bài 1: program bt1;
uses crt;
var n,d,k,S:integer;

begin
 clrscr; write('Nhap n: ');
 readln(n);
 while n<>0 do
  begin
   k:=n mod 10;
   n:=n div 10;
   S:=S+k;
   inc(d);
  end;
 writeln('n co ',d,' chu so');
 writeln('Tong cac chu so la: ',S);
 readln;
end.
Bài 2:

program bt2;
uses crt;
var n,i:integer;
    Kt:boolean;
    A:array[1..1000] of integer;
begin
 clrscr;
 readln(n);
 kt:=true;
 for i:=1 to n do read(A[i]);
 for i:=1 to n do
  if A[i]<>A[n-i+1] then
   begin
    kt:=false;
    break;
   end;
 if kt=true then writeln('Day la xau doi xung') else writeln('Day ko la xau doi xung');
 readln;
 readln;
end.

CAU 1:

uses crt;
var n,t,d:longint;
begin
clrscr;
readln(n);
while n<>0 do
begin
d:=d+1;
t:=t+n mod 10;
n:=n div 10;
end;
writeln('so luong chu so cua N = ',d);
writeln('tong cac chu so cua N = ',t);
readln
end.

CAU 2:

uses crt;
var n,i,j,k:longint;
a:array[1..100000] of longint;
kt:boolean;
begin
clrscr;
kt:=true;
readln(n);
for i:=1 to n do read(a[i]);readln;
if n mod 2 = 0 then k:=n div 2 else k:=(n+1) div 2;
i:=1;j:=n;
while i<=k+1 do
while j>=k-1 do
begin
if a[i]=a[j] then kt:=true
else
begin
kt:=false;
break;
end;
i:=i+1;j:=j-1;
end;
if kt=true then writeln('doi xung') else writeln('khong doi xung');
writeln(k);
readln
end.