The hatching period of the goose is 30 days, (4/5) of the hatching period of the goose is equal to the hatching period of the duck; the hatching period of the chicken is (3/4) of the duck. How many days does it take for a chicken to hatch?
鹅的孵化期是30天，鹅的孵化期的(4/5)等于鸭的孵化期；鸡的孵化期是鸭的(3/4)．鸡的孵化期是多少天？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

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

<gadget id="calculator">30 * (4/5) * (3/4)</gadget>
<output>18</output>

<result>18</result>