Uncle Li read a storybook and read 135 pages in 3 days. According to this calculation, it took another 4 days to read this storybook. How many pages does this storybook have? (Solve with ratio)
李叔叔看一本故事书，3天看了135页，照这样计算，又用了4天看完这本故事书，这本故事书一共有多少页？(用比例解)
<gadget id="calculator">135 / 3</gadget>
<output>45</output>

<gadget id="calculator">45 * 3</gadget>
<output>135</output>

<gadget id="calculator">45 * 4</gadget>
<output>180</output>

<gadget id="calculator">135 + 180</gadget>
<output>315</output>

<result>315</result>