There were about 360 species of fish in Dongshan Town, but due to various reasons such as environmental pollution, there are now about 270 species left. How many percent have the species decreased from the original?
东山镇原有鱼类约360种，由于环境污染等多种原因，现在约剩下了270种，种类比原来减少了百分之几？
<gadget id="calculator">360 - 270</gadget>
<output>90</output>

<gadget id="calculator">90 / 360</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>