The number of hens is more than that of roosters (2/5), the number of ducks is more than that of hens (4/7), what fraction of the number of ducks is that of roosters?
母鸡只数比公鸡多(2/5)，鸭的只数是母鸡的(4/7)，鸭的只数是公鸡的几分之几？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 + (2/5)</gadget>
<output>7/5 = around 1.4</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">(4/7) / 1</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 * (7/5) * (4/7)</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>