A batch of books has been repaired, 30 books have been repaired, which is 25% of the number of unrepaired books. How many books are there in total?
修补一批图书，已经修补了30本，是未修补本数的25%．这批图书一共多少本？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">30 / (1/4)</gadget>
<output>120</output>

<gadget id="calculator">120 + 30</gadget>
<output>150</output>

<result>150</result>