There is an open space of 1.5 hectares in Waterside Star City, where 12 buildings are planned to be built, each building covers an area of 900 square meters, and the rest is used for roads and greening. How many hectares are there total roads and green areas?
水岸星城有一块1.5公顷的空地，准备建12幢楼房，每幢楼房占地900平方米，剩下的用于道路和绿化．道路和绿化面积一共有多少公顷？
<gadget id="calculator">12 / 10_000</gadget>
<output>3/2_500 = around 0.0012</output>

<gadget id="calculator">900 * (3/2_500)</gadget>
<output>27/25 = around 1.08</output>

<gadget id="calculator">1.5 - (27/25)</gadget>
<output>0.42</output>

<result>0.42</result>