The survival rate of a kind of sapling is 90% through the test. In order to ensure 450 saplings survive, at least how many saplings should be planted.
一种树苗经试验成活率是90%，为了保证成活450棵，至少要栽种多少棵树苗．
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">450 / (9/10)</gadget>
<output>500</output>

<result>500</result>