program baitap;
uses crt;
var cv,s,a,b:integer;
begin
clrscr;
a := 12;
b := 8;
cv := (a+b)*2;
s := a*b;
writeln('Chu vi HCN = ',cv);
writeln('Dien tich HCN = ',s);
readln;
Bài 3:
#include <bits/stdc++.h>
using namespace std;
double a,b;
int main()
{
cin>>a>>b;
cout<<fixed<<setprecision(2)<<a*b;
return 0;
}