After cutting off 20% of a rope, and then connecting another 9 meters, the result is 10% longer than the original rope. How many meters was the original length of the rope?
一根绳子剪去20%以后，再接上9米结果比原来的绳子长10%，这根绳子原来长多少米？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/5) + (1/10)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">9 / (3/10)</gadget>
<output>30</output>

<result>30</result>