For an article, Mr. Song has already typed 1600 words, exactly 40% of the full text. How many words are there in the full text?
一篇文章，宋老师已经打了1600个字，正好打了全文的40%，全文共有多少个字？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1_600 / (2/5)</gadget>
<output>4_000</output>

<result>4_000</result>