\[\boxed{\text{1170\ (1170).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\overline{\text{ab}} \cdot \overline{\text{cd}} = \overline{\text{ad}} \cdot \overline{\text{cb}}\]
\[(10a + b)(10c + d) =\]
\[= (10a + d)(10c + b)\]
\[10a + b = 10a + d\ \ \ и\ \ \]
\[\ 10a + d = 10c + b\]
\[b = d,\ \ тогда\ \ \ \ \ \ \ \ \]
\[\ \ \ \ \ \ \ \ \ \ 10a = 10c,\ \ a = c\]
\[Ответ:при\ b = d\ или\ a = c.\ \]