Scientific irrigation methods can save water. The 17-hectare cotton experimental field used to be irrigated and used 2,700 tons of water at a time; after sprinkler irrigation, it used 850 tons of water at a time; now it uses drip irrigation and uses 323 tons of water at a time. How many tons of water can be saved per square meter by drip irrigation compared with sprinkler irrigation?
科学的灌溉方式可以节水．17公顷的棉花实验田原来采用浇灌的方式，一次用水2700吨；采用喷灌后，一次用水850吨；现在采用滴灌方式，一次用水323吨．采用滴灌方式平均每平方米比采用喷灌节约用水多少吨？
<gadget id="calculator">17 * 10_000</gadget>
<output>170_000</output>

<gadget id="calculator">850 / 170_000</gadget>
<output>1/200 = around 0.005</output>

<gadget id="calculator">323 / 170_000</gadget>
<output>19/10_000 = around 0.0019</output>

<gadget id="calculator">(1/200) - (19/10_000)</gadget>
<output>31/10_000 = around 0.0031</output>

<result>31/10_000 = around 0.0031</result>