One goose can be exchanged for 2 ducks, 5 pigeons can be exchanged for 1 duck, then how many pigeons can 2 geese exchange for?
一只鹅可以换2只鸭，5只鸽子可以换1只鸭，那么2只鹅可以换多少鸽子．
<gadget id="calculator">2 * 2 * 5</gadget>
<output>20</output>

<result>20</result>