A farm raises 800 ducks, but the number of chickens is less than that of ducks (1/5). How many chickens are there?
一个饲养场，养鸭800只，养的鸡比鸭少(1/5)，养的鸡有多少只？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">800 * (4/5)</gadget>
<output>640</output>

<result>640</result>