tìm tất cả các số có ba chữ số sao cho tích 3 chữ só bằng tổng 3 chữ số
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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.
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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
Đừng lấy bài của thằng Nyễn Khắc Vinh , nó lúc nào cũng 4545 , ko thì 454 , ....
Tổng 3 chữ số của số bé nhất có 3 chữ số có tích 3 chữ số bằng 3 là ?