The farm raises 420 beef cattle, which is less than the number of dairy cows (1/7). How many cows are raised?
养殖场养了420头肉牛，比养的奶牛少(1/7)，养了多少头奶牛？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 - (1/7)</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">420 / (6/7)</gadget>
<output>490</output>

<result>490</result>