Xiaopang reads a book and reads 72 pages in 6 days. According to this calculation, he can finish reading in 18 days. How many pages does this book have?
小胖读一本书，6天读了72页，照这样计算，18天可以读完，这本书有多少页？
<gadget id="calculator">72 / 6</gadget>
<output>12</output>

<gadget id="calculator">12 * 18</gadget>
<output>216</output>

<result>216</result>