program cau1;

uses crt;
var a,b,s,cv:longint;
begin
 clrscr;
  write('a=');readln(a);
  write('b=');readln(b);
  cv:=(a+b)*2;
  s:=a*b;
  writeln('chu vi hinh chu nhat la',cv);
  write('dien tich hinh chu nhat la:',s);
 readln;
end.

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program cau2;
uses crt;
var a,b,c,cv,h:longint;s:real;
begin
 clrscr;
  write('a=');readln(a);
  write('b=');readln(b);
  write('c=');readln(c);
  write('h=');readln(h);
  cv:=a+b+c;
  s:=h*a/2;
  writeln('chu vi hinh tam giac la:',cv);
  write('dien tich hinh tam giac la:',s);
 readln;
end.

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program cau3;
uses crt;
var y,x:longint;
begin
 clrscr;
  write('x=');readln(x);
  write('y=');readln(y);
  Writeln('Khoang cach: ',x*y/2);
 readln;
end.

-----------------------------------------

program cau4;

uses crt;
var a,b,c,tong,tich:longint;tbc:real;
begin
 clrscr;
  tong:=0;
  tich:=0;
  tbc:=0;
  write('a=');readln(a);
  write('b=');readln(b);
  write('c=');readln(c);
  tong:=a+b+c;
  tich:=a*b*c;
  tbc:=tong /3;
  writeln('tong cua 3 so la:',tong);
  writeln('tich cua 3 so la:',tich);
  write('trung binh cong cua 3 so la:',tbc);
 readln;
end.

Bài 1:
var cd,cr:longint;
begin
write('Nhap vao chieu dai = ');readln(cd);
write('Nhap vao chieu rong = ');readln(cr);
writeln('Chu vi HCN = ',(cd+cr)*2);
writeln('Dien tich HCN = ',(cd*cr));
readln;
end. 

Bài 2:
var h,a:longint;
    s:real;
begin
write('Nhap vao chieu cao = ');readln(h);
write('Nhap vao canh day = ');readln(a);
s :=(h*a)*1/2; 
writeln('Dien tich tam giac = ',s:0:2);
readln;
end.

Bài 3:
var x,y:longint;
    A:real;
begin
write('Nhap vao toa do x = ');readln(x);
write('Nhap vao toa do y = ');readln(y);
A := sqrt(sqr(x)+sqr(y));
writeln('Khoang cach = ',A:0:2);
readln;
end.

Bài 4:
var a,b,c:longint;
    tbc:real;
begin
write('Nhap vao a = ');readln(a);
write('Nhap vao b = ');readln(b);
write('Nhap vao c = ');readln(c);
tbc := (a+b+c)/3;
writeln('Trung binh cong = ',tbc:0:2);
readln;
end.