There are 2 red balls, 3 yellow balls and 5 white balls in a box. What is the probability of touching the red ball?
盒子里装了2个红球、3个黄球、5个白球．摸到红球的可能性是多少．
<gadget id="calculator">2 + 3 + 5</gadget>
<output>10</output>

<gadget id="calculator">2 / 10</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>