Bài 65:
program so_3chuso;
uses crt;
var n,i,a,d:longint;
begin
clrscr;
write('Nhap n: '); readln(n);
d:=0;
for i:=1 to n do
begin
write('Nhap so thu ',i,': '); readln(a);
if (a>=100) and (a<=999) then d:=d+1; {số dương có 3 chứ số}
if (a>=-999) and (a<=-100) then d:=d+1; {số âm có 3 chứ số}
end;
write('Co ',d,' so co ba chu so');
readln;
end.
Bài 66:
program khongqua_3chuso;
uses crt;
var n,i,a,d:longint;
begin
clrscr;
write('Nhap n: '); readln(n);
d:=0;
for i:=1 to n do
begin
write('Nhap so thu ',i,': '); readln(a);
if (a<=999) and (a>=-999) then d:=d+1;
end;
write('Co ',d,' so co khong qua ba chu so');
readln;
end.
Bài 67:
program so_3chuso;
uses crt;
var n,i,a,d,t:longint;
begin
clrscr;
write('Nhap n: '); readln(n);
d:=0; t:=0;
for i:=1 to n do
begin
write('Nhap so thu ',i,': '); readln(a);
if ((a>=100) and (a<=999)) or ((a>=-999) and (a<=-100)) then
begin
d:=d+1;
t:=t+a;
end;
if d=0 then write('-1')
else write('Trung binh cong cac so co 3 chu so la: ',t/d:0:3);
readln;
end.
Bài 68:
program tong_vitri_chan;
uses crt;
var n,i,a,t:longint;
begin
clrscr;
write('Nhap n: '); readln(n);
t:=0;
for i:=1 to n do
begin
write('Nhap so thu ',i,': '); readln(a);
if i mod 2=0 then t:=t+a;
end;
write('Tong cac so o vi tri chan la: ',t);
readln;
end.
