The lifespan of a lion is about 21 years, the lifespan of a tiger is that of a lion (19/21), and the lifespan of a hedgehog is that of a tiger (5/19). How many years does a hedgehog live?
狮子的寿命大约是21年，老虎的寿命是狮子的(19/21)，刺猬的寿命是老虎的(5/19)，刺猬的寿命是多少年？
<gadget id="calculator">19 / 21</gadget>
<output>19/21 = around 0.904762</output>

<gadget id="calculator">5 / 19</gadget>
<output>5/19 = around 0.263158</output>

<gadget id="calculator">21 * (19/21) * (5/19)</gadget>
<output>5</output>

<result>5</result>