Gọi số đó là abc ta có abc=a+b+c. Giả sử \(9\ge a\ge b\ge c\ge0\) thì \(abc=a+b+c\le3a\) suy ra \(bc\le3\)

abc khác 0 (vì \(a\ge1\) nên a+b+c\(\ge1\))

bc=3 thì b=3, c=1, suy ra 3+1+a=3a suy ra a=2 (loại, vì a bé hơn b)

bc=2 => b=2, c=1 suy ra 3+a=2a suy ra a=3 (Chọn)

bc=1 => b=1, c=1 suy ra 2+a=a (loại)

Vậy Các số cần tìm là 123, 132, 213, 231, 312, 321

uses crt;

var a,b,c:integer;

begin

clrscr;

for a:=1 to 9 do 

for b:=0 to 9 do 

for c:=0 to 9 do 

if (a+b+c=a*b*c) then writeln(a,b,c,' ');

readln;

end.

Tổng 3 chữ số của số bé nhất có 3 chữ số có tích 3 chữ số bằng 3 là ? 

102;111;120;201;210;300.

102;111;120;201;210;300;

102 , 111 , 120, 201, 210, 300

Làm thế nào vậy ???

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địt lồn mẹ mày bú buồi đầu buồi liếm lông chim

Số có 3 chữ số có dạng \(\overline{abc}\)

Trong đó \(a\) có 3 cách chọn

               \(b\) có 2 cách chọn

               \(c\) có 1 cách chọn 

Số các số có 3 chữ số mà mỗi số có đủ ba chữ số trên và mỗi chữ số chỉ xuất hiện một lần là:

              3 \(\times\) 2 \(\times\) 1 = 6 (số)

Các chữ số: 3; 5; 1 xuất hiện số lần như nhau ở các hàng trăm, hàng chục, hàng đơn vị và xuất hiện số lần là:

               6 : 3 =  2 (lần)

Tổng các chữ số vừa được lập ở trên là:

     (1 + 3 + 5) \(\times\)(100 + 10+1)\(\times\)2 = 1998

Đáp số: 1998

Các số tự nhiên có ba chữ số khác nhau tạo thành từ ba chữ số 3;7;2 là:

237; 273; 327; 372; 723; 732

Tổng của Các số tự nhiên có ba chữ số khác nhau tạo thành từ ba chữ số 3;7;2 là:

237+273+327+372+723+732

=510+699+1455

=2664

a)a25,25a,52a,2a5,5a2,a52

bạn mới giải câu a còn câu b chưa giải