Uncle Zhang raised 300 geese, and the number of geese was less than the number of ducks (2/5). How many ducks do you have?
张大爷养了300只鹅，鹅的只数比鸭的只数少(2/5)．养了多少只鸭？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">300 / (3/5)</gadget>
<output>500</output>

<result>500</result>