Đáp án đúng: A
Giải chi tiết:\(\begin{array}{l}401 - \overline {ab} = \overline {ab5} \\401 - \overline {ab} = \overline {ab} \times 10 + 5\\401\,\,\,\,\,\,\,\,\,\,\,\, = 10 \times \overline {ab} + \overline {ab} + 5\\401 - 5\,\,\,\,\, = 11 \times \overline {ab} \\396\,\,\,\,\,\,\,\,\,\,\,\, = 11 \times \overline {ab} \\\overline {ab} \,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 396:11\\\overline {ab} \,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 36.\end{array}\)
Chọn A.