A certain large tea family planted 450 tea trees last year, and 405 trees survived. According to this calculation, to ensure that 450 trees will survive this year, how many trees should be planted at least?
某种茶大户，去年种茶450棵，成活405棵，照这样计算，今年要保证成活450棵，至少应种多少棵？
<gadget id="calculator">405 / 450</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">(9/10) * 1</gadget>
<output>9/10 = around 0.9</output>

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

<result>500</result>