There are 210 chickens, and the ratio of the number of chickens to the number of ducks is 2:5. How many ducks are there?
鸡有210只，鸡的只数和鸭的只数比是2：5．鸭有多少只？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">210 / (2/5)</gadget>
<output>525</output>

<result>525</result>