There is a box containing 5 red balls, 3 white balls, and 2 black balls (the balls are only different in color), what is the probability of drawing a red ball from it at a time?
有一个装有5个红色小球，3个白色小球，2个黑色小球(小球仅是颜色不同)的盒子，从中一次摸出一个红色小球的可能性大小是多少．
<gadget id="calculator">5 + 3 + 2</gadget>
<output>10</output>

<gadget id="calculator">5 / 10</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>