There are 1 white ball, 2 red balls, and 6 black balls in a box. If you touch any one, what is the probability of getting a black ball?
盒子里装有1个白球、2个红球、6个黑球，任意摸一个，摸到黑球的可能性是多少．
<gadget id="calculator">1 + 2 + 6</gadget>
<output>9</output>

<gadget id="calculator">6 / 9</gadget>
<output>2/3 = around 0.666667</output>

<result>2/3 = around 0.666667</result>