There are several kilograms of rice, take out (1/2) of it each time, take out the rest (1/3) for the second time, and take out the rest (1/4) for the third time, and take it out in this way, and take 1989 After the second time, there is 1 kg of rice left. How many kilograms of rice is there?
有大米若干千克，每一次取出它的(1/2)，第二次取出余下的(1/3)，第三次取出再余下的(1/4)，照这样依次取下去，取了1989次以后，还剩大米1千克．原来有大米多少千克？
<gadget id="calculator">1 / 1_990</gadget>
<output>1/1_990 = around 0.000503</output>

<gadget id="calculator">1 / (1/1_990)</gadget>
<output>1_990</output>

<result>1_990</result>