Bài 1: 

uses crt;

var a:array[1..200]of integer;

i,n,t:integer;

begin

clrscr;

write('Nhap n='); readln(n);

for i:=1 to n do 

begin

write('A[',i,']='); readln(a[i]);

end;

t:=0;

for i:=1 to n do 

  if a[i] mod 5=0 then t:=t+a[i];

writeln('Tong cac so chia het cho 5 la: ',t);

readln;

end.

Bài 2: 

uses crt;

var st:string;

d,i:integer;

begin

clrscr;

write('Nhap xau:'); readln(st);

d:=length(st);

for i:=1 to d do 

  if st[i]=#32 then delete(st,i,1);

writeln(st);

readln;

end.

Uses crt;

Var m,n,i,s: longint;

Begin clrscr;

Write ('nhap m:'); readln (m);

Write ('nhap n:'); readln (n);

While n <m do

Begin

Write ('nhap lai n:');

Readln (n);

End;

S:=0;

For i:=m to n do

If (i mod 3=0) or (i mod 5=0) then s:=s+i;

Write(s);

Readln;

end.

Chỗ câu lệnh if thì mình dùng if (i mod 3 = 0) and (i mod 5 = 0) nhé em! Không dùng or sẽ bị sai

uses crt;

var n,i,t:integer;

begin

clrscr;

repeat

write('Nhap n='); readln(n);

until n>0;

t:=0;

for i:=1 to n do 

  if i mod 3=0 then t:=t+i;

writeln('Tong cac so chia het cho 3 trong khoang tu 1 toi ',n,' la: ',t);

readln;

end.

#include <bits/stdc++.h>

using namespace std;

long long m,n,i,t;

int main()

{

cin>>m>>n;

t=0;

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

if (i%15==0) t=t+i;

cout<<t;

return 0;

}

uses crt;

var a:array[1..100]of integer;

i,n,t:integer;

begin

clrscr;

write('Nhap n='); readln(n);

for i:=1 to n do 

begin

write('A[',i,']='); readln(a[i]);

end;

for i:=1 to n do 

  write(a[i]:4);

writeln;

t:=0;

for i:=1 to n do 

  if a[i] mod 7=0 then t:=t+a[i];

writeln('Tong cac so chia het cho 7 la: ',t);

readln;

end. 

Bài 2: 

#include <bits/stdc++.h>;

using namespace std;

int main();

{

long m,n;

cout<<"Nhap m="; cin>>m;

cout<<"Nhap n="; cin>>n;

cout<<m*n-2;

return 0;

}

Var i,n:integer;

s:longint;

Begin

Write('n = ');readln(n);

For i:=1 to n-1 do

If (i mod 2 = 0) and (i mod 3 = 0) then

s:=s + i;

Write('Tong la ',s);

Readln;

End.

uses crt;

var i,n,dem:integer;

begin

clrscr;

repeat

write('Nhap n='); readln(n);

until n>0;

writeln('Cac so chan va chia het cho 4 trong khoang tu 5 toi ',n,' la: ');

for i:=5 to n do 

  if (i mod 2=0) and (i mod 7=0) then write(i:4);

writeln;

writeln('Cac so chia het cho 7 trong khoang tu 5 toi ',n,' la: ');

dem:=0;

for i:=5 to n do 

  if i mod 7=0 then 

   begin

write(i:4);

inc(dem);

end;

writeln;

writeln('Co ',dem,' so chia het cho 7 trong khoang tu 5 toi ',n);

readln;

end.