A book has 120 pages, and 25% of it has been read, how many pages should be read from when reading again.
一本书120页，已读过它的25%，再读时应从多少页读起．
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">120 * (1/4)</gadget>
<output>30</output>

<gadget id="calculator">30 + 1</gadget>
<output>31</output>

<result>31</result>