To make a batch of parts, it was planned to be completed in 20 days, but it was actually completed in 16 days. How much has the construction period been shortened?
做一批零件，计划20天完成，实际16天就完成了，工期缩短了多少
<gadget id="calculator">20 - 16</gadget>
<output>4</output>

<gadget id="calculator">4 / 20</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>