lǎo / shī / zài / kè / táng / shàng / yòng / Lā / dīng / fāng / kuài / jiǎng / jiě / pái / liè / zǔ / hé

老师在课堂上用拉丁方块讲解排列组合。

The teacher used Latin squares in class to explain permutations and combinations.