A new batch of books has been added to the school library, a total of 2,400 books. Science fiction books account for (11/20), reasoning books account for (19/60), and the rest are story books. Please ask two mathematical problems and try to solve them.
学校图书馆新进了一批书，共2400本，科幻类的占(11/20)，推理类的占(19/60)，剩下的都是故事类的．请你提出两个数学问题，并尝试解答．
<gadget id="calculator">11 / 20</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">19 / 60</gadget>
<output>19/60 = around 0.316667</output>

<gadget id="calculator">(11/20) + (19/60)</gadget>
<output>13/15 = around 0.866667</output>

<gadget id="calculator">2_400 * (13/15)</gadget>
<output>2_080</output>

<result>2_080</result>