Every time half of the toys in the toy store are sold, 20 more toys will be added. After the tenth half of the toys are sold, there will be exactly 20 remaining toys. What is the number of toys in the toy store?
玩具店的玩具每卖出一半，就补充20个，到第十次卖出一半后恰好余下20个，则玩具店原有玩具多少个．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">20 / (1/2)</gadget>
<output>40</output>

<result>40</result>