From 7 o'clock to 11 o'clock, Li Ming processed a total of 228 parts. How many parts does he process per hour on average?
李明从7时到11时，共加工了228的零件，他平均每小时加工零件多少个．
<gadget id="calculator">11 - 7</gadget>
<output>4</output>

<gadget id="calculator">228 / 4</gadget>
<output>57</output>

<result>57</result>