The school distributes 72 general undergraduate textbooks to Classes A and B at a ratio of 4:5. How many books will Class A get?
学校把72本科普读物，按4：5分配给A、B两个班，A班分得多少本．
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">72 * (4/9)</gadget>
<output>32</output>

<result>32</result>