Câu 1:
uses crt;
var i,n: integer;
s: longint;
begin
clrscr;
write ('nhap n: '); readln (n);
for i:=1 to (2*n-1) do
if i mod 2=0 then s:=s+i;
writeln ('tong s= ',s);
readln;
end.
Câu 3:
uses crt;
var a: array[1..100] of longint;
i,n: integer;
d: byte;
s: word;
tb: real;
begin
clrscr;
write ('nhap n: '); readln (n);
for i:=1 to n do
begin
write ('nhap phan tu thu ',i,': '); readln (a[i]);
if a[i]>0 then begin inc(d); s:=s+a[i]; end;
end;
tb:=s/d;
writeln ('trung binh cac so duong trong mang la: ',tb:1:2);
readln;
end.
