A batch of sneakers was shipped in to the mall, 18% of the total sold in the first week, and 27% of the total sold in the second day, leaving 220 pairs unsold. How many pairs of this batch of sneakers are there?
商场运进一批运动鞋，第一周卖出总数的18%，第二天卖出总数的27%，还剩下220双没卖完，这批运动鞋一共有多少双？
<gadget id="calculator">18 / 100</gadget>
<output>9/50 = around 0.18</output>

<gadget id="calculator">27 / 100</gadget>
<output>27/100 = around 0.27</output>

<gadget id="calculator">1 - (9/50) - (27/100)</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">220 / (11/20)</gadget>
<output>400</output>

<result>400</result>