In science class, students weigh objects with a spring scale. When weighing 300 grams of objects, the length of the spring is 9 cm; when weighing 900 grams of objects, the length of the spring is 11 cm. How long is the spring when the object is not weighed?
科学课上，同学们用弹簧秤称物体，称300克的物体，弹簧长9厘米；称900克的物体，弹簧长11厘米，那么不称物体时弹簧长多少厘米？
<gadget id="calculator">11 - 9</gadget>
<output>2</output>

<gadget id="calculator">900 - 300</gadget>
<output>600</output>

<gadget id="calculator">2 / 600</gadget>
<output>1/300 = around 0.003333</output>

<gadget id="calculator">(1/300) * 300</gadget>
<output>1</output>

<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<result>8</result>