If a bag contains 4 white balls, 5 black balls and 6 light balls, and 4 balls are randomly selected, what is the probability that 3 black balls are contained?
一个袋中装有4个白球，5个黑球和6个光球，从中任取4个球，则含有3个黑球的概率为多少．
<gadget id="calculator">10 * 10</gadget>
<output>100</output>

<gadget id="calculator">100 / 1_365</gadget>
<output>20/273 = around 0.07326</output>

<result>20/273 = around 0.07326</result>