The master produces 60 parts per hour, and the apprentice produces 90 parts in 2 hours. How many hours does it take the apprentice to complete the parts produced by the master in 3 hours?
师傅每小时生产零件60个，徒弟2小时生产90个零件．师傅3小时生产的零件，徒弟要几小时完成？
<gadget id="calculator">90 / 2</gadget>
<output>45</output>

<gadget id="calculator">3 / 45</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">60 * (1/15)</gadget>
<output>4</output>

<result>4</result>