There are 4 red balls, 5 yellow balls and 6 black balls in the bag. If a ball is drawn at random, what is the probability of drawing a black ball?
袋中有4个红球，5个黄球，6个黑球．任意摸出1个球，摸到黑球的可能性是多少．
<gadget id="calculator">4 + 5 + 6</gadget>
<output>15</output>

<gadget id="calculator">6 / 15</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>