Naughty reading a 420-page story book, I have read 40% of the whole book, how many pages are left?
淘气看一本420页的故事书，已经看完了全书的40%，还有多少页没有看？
<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">420 * (3/5)</gadget>
<output>252</output>

<result>252</result>