Master Wang and Master Zhang cooperated to process 40 parts. Master Wang made 15 parts per hour, Master Zhang made 20 parts per hour, and Master Wang made 1.6 hours. How many hours did Master Zhang make?
王师傅和张师傅合作加工40个零件，王师傅每小时做15个，张师傅每小时做20个，王师傅做了1.6小时，张师傅做了多少小时？
<gadget id="calculator">15 * 1.6</gadget>
<output>24</output>

<gadget id="calculator">40 - 24</gadget>
<output>16</output>

<gadget id="calculator">16 / 20</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>