Mom bought back a spring with a 10kg (elasticity limit) object in the wire tube. Xiaogang was curious and tried it out, and found that the length of the spring would elongate after the object was hung on it. Xiaogang tried again, and found that if the spring is hung with a 4 kg object, the length of the spring is 22 cm; if a 6 kg object is hung, the length of the spring is 23 cm. Within the elastic limit, the length of the spring elongation is proportional to the mass of the hanging object. How many centimeters is the length of the spring if no object is hung on it?
妈妈买回一根线管10千克(弹性限度)物体的弹簧，小刚很好奇动手试了试，发现弹簧挂上物体后长度会伸长．小刚又试了试，还发现这个弹簧若挂上4千克物体，则弹簧长22厘米；若挂上6千克物体，则弹簧长23厘米．在弹性限度内，弹簧伸长的长度与所挂物体的质量成正比例．若不挂物体，则这根弹簧长多少厘米？
<gadget id="calculator">6 * 22</gadget>
<output>132</output>

<gadget id="calculator">4 * 22</gadget>
<output>88</output>

<gadget id="calculator">4 * 23</gadget>
<output>92</output>

<gadget id="calculator">88 - 88 - 92</gadget>
<output>-92</output>

<gadget id="calculator">132 + (-92)</gadget>
<output>40</output>

<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<result>20</result>