Câu 1: 

Dùng for..do

uses crt;

var a,i:integer;

begin

clrscr;

a:=0;

for i:=1 to 100 do 

  if i mod 2=0 then a:=a+i;

writeln(a);

readln;

end.

Dùng While...do

uses crt;

var a,i:integer;

begin

clrscr;

a:=0;

i:=1;

while i<=100 do 

  begin

if i mod 2=0 then a:=a+i;

inc(i);

end;

writeln(a);

readln;

end.

#include <bits/stdc++.h>

using namespace std;

long long n,i,x,dem;

int main()

{

cin>>n;

dem=0;

for (i=1; i<=n; i++)

{

cin>>x;

if (x%2==0) dem++;

}

cout<<dem;

return 0;

}

#include <bits/stdc++.h>

using namespace std;

long long x,i,n,dem;

int main()

{

cin>>n;

dem=0;

for (i=1; i<=n; i++)

{

cin>>x;

if (x%2==0) dem++;

}

cout<<dem;

return 0;

}

Uses crt;

var i,n: integer;

begin clrscr;

readln(n);

for i:=1 to n do if(i mod 2<>0) then writeln(i);

readln;

end.

số nguyên n nhập từ bàn phím anh ơi

#include <bits/stdc++.h>

using namespace std;

int n,i,x,dem;

int main()

{

cin>>n;

dem=0;

for (i=1; i<=n; i++)

{

cin>>x;

if (x%2==0) dem++;

}

cout<<dem;

return 0;

}

Bài 4

uses crt;
var a,b: integer;
c,s,d:real;
begin
clrscr;
readln(a,b);
if (a>0) and (b>0) then
begin
c:=sqrt(a*a+b*b);
d:=(a+b+c)/2;
s:=sqrt(d*(d-a)*(d-b)*(d-c));
writeln(c:4:2,'  ',s:4:2);
end
else writeln('nhap lai');
readln
end.

Bài 5

uses crt;
var r: integer;
s,t: real;
begin
clrscr;
readln(r);
s:=r*r*3.14;
t:=2*3.14*r;
writeln(s:4:2,'  ',t:4:2);
readln
end.