There are 280 goats in a farm, which is the number of sheep (4/7). How many sheep are there?
某农场有山羊280只，是绵羊只数的(4/7)．绵羊有多少只？
<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">280 / (4/7)</gadget>
<output>490</output>

<result>490</result>