A product is composed of one large part and two small parts. It is known that the master can produce 9 large parts or 14 small parts per hour, and the apprentice can produce 3 large parts or 10 small parts per hour. If 27 sets of this product are to be produced, how many hours must the master and apprentice work together at least.
一种产品是由一个大零件和两个小零件组成，已知师傅每小时可生产9个大零件或者14个小零件，徒弟每小时可生产3个大零件或者10个小零件．如果要生产27套这种产品，那么师、徒两人至少需要合作多少小时．
<gadget id="calculator">9 + 3</gadget>
<output>12</output>

<gadget id="calculator">27 / 12</gadget>
<output>9/4 = around 2.25</output>

<gadget id="calculator">(9/4) * 2</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>