Xiaohong reads a book and reads 15 pages every day. She reads (2/5) of the whole book in 4 days. How many pages does this book have?
小红看一本书，每天看15页，4天共看了全书的(2/5)，这本书有多少页？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">4 / (2/5)</gadget>
<output>10</output>

<gadget id="calculator">15 * 10</gadget>
<output>150</output>

<result>150</result>