The sixth grade office bought a pack of white paper. It was planned to use 20 sheets per day, and it could be used for 28 days. In fact, only 16 sheets were used per day. How many days did the pack of paper actually use?
六年级办公室买进一包白纸，计划每天用20张，可以用28天，实际每天只用了16张，这包纸实际用了多少天？
<gadget id="calculator">28 / 16</gadget>
<output>7/4 = around 1.75</output>

<gadget id="calculator">20 * (7/4)</gadget>
<output>35</output>

<result>35</result>