Master Zhang produces 28 parts in 4 hours, so calculate how many hours it will take to produce 84 parts.
张师傅4小时生产28个零件，照这样计算要生产84个零件需要多少小时．
<gadget id="calculator">28 / 4</gadget>
<output>7</output>

<gadget id="calculator">84 / 7</gadget>
<output>12</output>

<result>12</result>