Ducks in Xingwang Farm account for 30% of the total number of poultry, and hens account for 20% of the total number of poultry. How much more ducks are there than hens?
兴旺饲养场的母鸭占禽类总数的30%，母鸡占禽类总数的20%，母鸭比母鸡多多少．
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(3/10) - (1/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) / (1/5)</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>