If someone reads a book with 200 pages and reads 40% of the book, how many pages are left in the book?
某人看一本共200页的书，看了全书的40%，那么此书还剩多少页没看．
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">200 * (3/5)</gadget>
<output>120</output>

<result>120</result>