The ratio of books in classes A and B is 7:4. Class A has 280 books, how many books does Class B have?
甲、乙两个班图书本数比是7：4．甲班有图书280本，乙班有图书多少本．
<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">280 * (4/7)</gadget>
<output>160</output>

<result>160</result>