1)
program tongA;
uses crt;
var n,i: integer; A: real;
Begin
clrscr;
write('nhap n: '); readln(n);
for i:=1 to n do A:=A+1/(i*(i+2));
write('A = ',A:2:2);
readln
End.
2)
program tongB;
uses crt;
var i,B: integer;
Begin
clrscr;
for i:=1 to 100 do
if i mod 2=0 then B:=B+i;
write('B = ',B);
readln
End.
3)
program tongC;
uses crt;
var i: integer; C: real;
Begin
clrscr;
for i:=1 to 50 do C:=C+1/i;
write('C = ',C:2:2);
readln
End.
