program Tinh_tong ;

var n,i : interger ;

      S : longint ;

begin

write ('Nhap so n = '); readln(n) ;

S:=0 ;

      for i := 1 to n do S :=S+i ;

writeln ('Tong cua n ' ,n, ' so tu nhien dau tien S = ' ,S) ;

readln ; 

end
Câu 9:
uses crt;
var n,i:integer;
kq,x: real;
begin
clrscr;
write('Nhap N: ');readln(n);
i:= 0; kq:= 0;
while i < n do
begin
i:= i + 1;
write('Nhap X ',i,': ');
readln(x);
kq:= kq + x;
end;
write('Trung binh ',n,' so thuc la: ',kq / n:0:2);
readln
end.
Chấm điểm cho mk nhé!
Cảm ơn bạn!