The germination experiment was done at the seed station. The germination rate of the seeds was 97.5%. To get 390 sprouts, how many seeds are needed.
种子站做发芽实验，种子的发芽率是97.5%，要得到390棵芽，需要种子多少粒．
<gadget id="calculator">97.5 / 100</gadget>
<output>0.975</output>

<gadget id="calculator">390 / 0.975</gadget>
<output>400</output>

<result>400</result>