Xiao Ming reads a story book, and reads the whole book (1/15) every day. After 3 days, there are 40 pages left to read. How many pages are there in this book?
小明读一本故事书，每天读全书的(1/15)，3天后还剩40页没有读，这本书一共有多少页？
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/15) * 3</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">40 / (4/5)</gadget>
<output>50</output>

<result>50</result>