Pack a batch of fruits into boxes. If 42 boxes are packed, 70% of the batch of fruits will be left. If 85 boxes are packed, there will be 1540 apples left. How many apples are there in this batch?
将一批水果装箱，如果装42箱，还剩下这批水果的70%，如果装85箱，还剩1540个苹果，这批苹果共有多少个．
<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 - (7/10)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">42 / (3/10)</gadget>
<output>140</output>

<gadget id="calculator">140 - 85</gadget>
<output>55</output>

<gadget id="calculator">1_540 / 55</gadget>
<output>28</output>

<gadget id="calculator">28 * 140</gadget>
<output>3_920</output>

<result>3_920</result>