Master Zhang produced 840 parts in 7 days, and he worked 8 hours a day. How many parts does Master Zhang produce on average per hour?
张师傅7天生产了840个零件，他每天工作8小时．张师傅平均每小时生产多少个零件？
<gadget id="calculator">840 / 7</gadget>
<output>120</output>

<gadget id="calculator">120 / 8</gadget>
<output>15</output>

<result>15</result>