Zhang Qiang reads a 100-page technical book. He reads 1/4 of the total pages in the morning and 20% of the total pages in the afternoon. How many pages are left unread?
张强看一本100页的科技书，上午看了总页数的(1/4)，下午看了总页数的20%，还余下多少页没有看？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/4) - (1/5)</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">100 * (11/20)</gadget>
<output>55</output>

<result>55</result>