6 kg of salt can be produced from 300 kg of seawater, how many tons of seawater are needed to produce 300 kg of salt?
300千克海水可以制盐6千克，要制300千克的盐，需要海水多少吨．
<gadget id="calculator">300 * 0.3</gadget>
<output>90</output>

<gadget id="calculator">90 / 6</gadget>
<output>15</output>

<result>15</result>