If 1 cow is exchanged for 6 pigs, 2 pigs are exchanged for 4 sheep, 3 sheep are exchanged for 20 chickens, how many cows can be exchanged for 400 chickens?
1头牛换6头猪，2头猪换4只羊，3只羊换20只鸡，400只鸡可换多少头牛．
<gadget id="calculator">400 / 20</gadget>
<output>20</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">2 / 6</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">20 * (3/4) * (1/3)</gadget>
<output>5</output>

<result>5</result>