During the Arbor Day, the school planted a memorial forest, and 180 trees survived, equivalent to 90% of the total number of trees planted. How many trees are there in this memorial forest?
植树节期间，学校栽了一片纪念林，有180棵成活，相当于植树总数的90%，这片纪念林一共有多少棵树？
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">180 / (9/10)</gadget>
<output>200</output>

<result>200</result>