a)
uses crt;
var n,i,s:integer;
begin
clrscr;
write('Nhap n: '); readln(n);
s:=0;
for i:=1 to n do
s:=s+i;
write('S= ',s);
readln;
end.
b)
uses crt;
var n,i,s:integer;
begin
clrscr;
write('Nhap n: '); readln(n);
s:=0;
for i:=1 to n do
if i mod 2=1 then s:=s+i;
write('S= ',s);
readln;
end.
c)
uses crt;
var n,i:integer;
s:real;
begin
clrscr;
write('Nhap n: '); readln(n);
s:=0;
for i:=1 to n do
s:=s+1/i;
write('S= ',s:0:3);
readln;
end.
d)
uses crt;
var n,i:integer;
s:real;
begin
clrscr;
write('Nhap n: '); readln(n);
s:=0;
for i:=2 to n do
s:=s+1/((i-1)*i);
write('S= ',s:0:3);
readln;
end.
